30-Second Verdict
Both of these scored 8.3/10 from me, and I stand by both numbers. Which means the winner isn't a score — it's a question: do you want the PAX that's lighter, faster to heat, clearly cheaper and easier to live with, or the PAX that actually hits? For most people, the PAX 4 is the right buy. I called it "the PAX you'd actually buy if you wanted one PAX" in the full review and nothing in six weeks of running both has changed my mind. The Flow is for the buyer who wants PAX design and proper vapour, and is willing to pay Mighty+ money for the combination.
PAX 4: 8.3/10
PAX Flow: 8.3/10
Buy the PAX 4 if:
- You want the lightest, slimmest, most frictionless PAX — 125g, ~20-second heat-up, zero learning curve
- You're a solo user — the half-pack lid comes in the box, not on a separate order
- The PAX 4's price already feels like a lot for a pocket vape (it is; it's fine; it's PAX)
- You'd rather have real-time manual temperature nudging than five fixed modes
Buy the PAX Flow if:
- You want the strongest vapour PAX has ever produced — 8.5/10 against the PAX 4's 7.8
- Bong Mode matters to you — 225°C and a disabled motion sensor for water-pipe sessions
- The 20-minute half-charge fits your life (dinner-table top-up before going out)
- You're happy paying the premium for the tuned engine
Quick Specs:
| PAX 4 | PAX Flow | |
|---|---|---|
| Heat-up | ~20s (18–22s measured) | 25–35s |
| Battery | Sealed 2800mAh, ~5 sessions | Sealed 2000mAh, 4–6 sessions |
| Bowl | ~0.35g, half-pack lid included | ~0.4g, side-loading oven |
| Weight | 125g | 135g |
| Warranty | 2yrs, 3 with registration | 2yrs standard UK |
| Price | Check current price | Check current price |
The Hook: The Hatchback and the Hot Hatch
Walk into a Volkswagen dealership and there are two Golfs on the floor.
One is the Golf. The standard one. Quietly correct for fifty years — practical, handsome in an unshowy way, so easy to live with that you stop thinking about it within a week. Nobody has ever regretted buying a Golf. That's the whole brand.
The other one is the GTI. Same platform. Same badge. Same shape, if you squint. But somebody in the engineering department has been let off the leash — the engine breathes properly, the exhaust has opinions, and it costs a chunk more for the privilege. The GTI exists for the person who looked at the standard Golf and thought: yes, but faster.
The PAX 4 is the Golf. The PAX Flow is the GTI. Same platform, one tuned for airflow.
And I mean "same platform" almost literally. Same anodised aluminium, same one-button-and-haptics interface, same conduction-leaning hybrid heart, same USB-C (finally — a decade of proprietary dock nonsense, gone from both). Same 9.5/10 portability score. Same warm-grip problem at the top of the range, and the same cheeky silicone sleeve sold separately to fix it. These are siblings, not rivals.
I called the Flow the Take That comeback when I reviewed it — the Patience era, the record that made the critics put their knives away. The PAX 4 arrived after and did something quieter but arguably more important: it took the comeback and made it mainline. Dave gave up on his PAX 3 two years ago; his reaction to the Flow — "Wait, when did PAX stop being rubbish?" — is on record. The PAX 4 is what happens when they stay not-rubbish for a second consecutive device.
So the question isn't "which one is good." Both are good. Both scored 8.3. The question is the Golf question: do you actually need the GTI, or do you just like the idea of it?
We stock both at HerbVape.co.uk — details and pricing below.
Vapour Quality
PAX 4: 7.8/10 · PAX Flow: 8.5/10 — the Flow wins, clearly.
This is the tuned engine, and it's not subtle. PAX claims six times more airflow through the Flow's redesigned chamber, and for once the marketing isn't lying — the restricted-straw draw that defined a decade of PAX devices is genuinely gone. The Flow's hybrid heating extracts more evenly, stacks denser clouds at mid-temps, and puts it comfortably in conversation with the Veazy and Crafty+. That's company no PAX has ever kept before.
The PAX 4 runs the same architecture scaled down — the convection assist is doing more work than the PAX 3 ever managed, and it produces the best vapour of any non-Flow PAX. But it's the standard engine. Good vapour, not great vapour. Sip it and it delivers four to six properly flavoured draws; try to rip it and you get warm air and regret. Both devices are sippers, mind — the Flow just gives you more per sip.
Where the PAX 4 claws something back is at the edges: it heats faster (~20 seconds against the Flow's 25–35), and its real-time manual adjustment lets you nudge the temperature within the modes, which the Flow's five fixed presets don't. Precision versus power.
Honest winner: the Flow, by a well-tuned margin. If vapour quality is your first sorting criterion between these two, stop reading and buy the Flow. But do read the value section first.
The Strain Test, Side by Side
Same two jars, same grinder, same protocol — the strain is the control, so for once you can put two PAXes side by side and know the difference on the exhale is the machine. The Flow got 0.4g loads level to the lip of its side-loading oven; the PAX 4 got 0.35g with a firm level tamp, half-pack lid in the drawer. Each ran its own review ladder — 180/190/200°C on the Flow's modes, 180/193/205°C via the PAX 4's manual nudge.
Jack Herer
Jack is the strain that shows you up, and it shows both of these up — just to different degrees.
At 180°C the Flow gave me pine needles and lemon peel with a proper citrus lift, "brighter than any PAX has ever given me from this jar" — and the PAX 4 promptly answered with a first draw that was "better than any PAX has given me": pine, lemon peel, a thin thread of fresh resin. Draw one is a genuine dead heat, which tells you the shared airflow work is real. The separation happens next. The Flow held the brightness for two draws and thinned by four; the PAX 4 held most of it through draw two and had blended the citrus into general green warmth by draw three. The Flow's open chamber buys Jack roughly half a draw more life, and neither machine gets close to a glass stem.
Mid-temp, both converge on the same result via the same physics: black pepper arrives with definition — pepper is the durable heart of this flower and hot walls don't trouble it — laid over a woody haze. Four consistent draws each. And on both, the layering is gone: the Flow gives you "four draws, all satisfying, none of them diagnostic," the PAX 4 hands you pepper and wood "blended together rather than stacked." Same conduction tax, same till.
Top temp is earth and roast on both, three draws to an evenly browned bowl, nothing scorched. Twelve honest draws each. On Jack, the Flow wins narrowly — a cover version with slightly better production — but if terpinolene is what you buy vaporisers for, neither of these is your vaporiser, and I said exactly that in both reviews.
Wedding Cake
This is where both machines stop apologising, and where the price gap actually shows up in the vapour.
Low temp: vanilla and sweet cream arrive thick on both — the Flow's low mode kept the cherry edge distinct from the cream; the PAX 4 matched the sweetness and held it five draws without thinning, because dessert notes sit low and hot walls don't hurt them. Neither machine needs an apology on this strain, which is not a sentence I could have written about any two PAXes before 2026.
Mid-temp is the decider. On the Flow at 190°C, butter separates cleanly from dough, the cherry deepens towards jam, and I called that separation "the single most impressive thing this machine does." On the PAX 4 at 193°C, I could name vanilla, butter, dough and pepper as four separate things — "not what I expected from an oven at this price." Both resolve. The Flow resolves with more density behind it — the PAX 4 gives you the components; the Flow gives you the components with body. That gap is the 8.5 versus the 7.8, distilled into one draw.
By the top of the range both jars converge into the same brown roast on both devices, same as every hot-walled oven ever made.
The flavour-device/delivery-device call: the Flow is a delivery device with a flavour window — spectacular for the first third of a dessert bowl. The PAX 4 is half and half — good enough to separate vanilla from butter, not good enough to keep hold of pine. Both are dessert-strain machines. If your jar looks like the Wedding Cake jar, the Flow is the best conduction-leaning rendering I've had. If your jar looks like the Jack jar, save your money — on fragile terps these two are closer than the prices suggest, and neither is the answer.
Design & Build
PAX 4: 9.5/10 · PAX Flow: 9/10 — PAX 4, narrowly.
Same design language — polished-pebble aluminium, no visible screws, no seams, the only vapes in the shop that read as consumer electronics. The differences are executional. The PAX 4 is slimmer through the body, ten grams lighter, and to my eye the cleaner object; the Flow is denser and feels marginally more premium in the hand, but its interior carries more plastic than its price suggests, which cost it half a point in the review.
The Flow's party piece is the side-loading magnetic oven door — genuinely elegant, one-handed loading while walking. The PAX 4 counters with a slightly larger chamber opening than the Mini 2 and an included half-pack lid, which is the more useful trick if you mostly load at home before going out.
Both build heat in the grip at the top of the range — the Flow gets properly uncomfortable in Bong Mode, the PAX 4 merely warm at Mode 4 — and both want the sleeve PAX won't put in the box. Winner: PAX 4, for the cleaner interior and the lighter body, but this is a family resemblance argument, not a fight.
Battery & Charging
PAX 4: 7.5/10 · PAX Flow: 8/10 — the Flow, on charging speed.
Counterintuitive, this one. The PAX 4 has the bigger cell (2800mAh vs 2000mAh) and roughly matching endurance — about five sessions against the Flow's four to six. Neither is class-leading; the Solo 3 v2 does twelve to fifteen bowls and laughs at both.
The Flow wins because of what happens at the wall: 50% in 20 minutes, full in under 40. That's genuinely useful — a top-up in the time it takes to eat a starter. The PAX 4's 100-minute full charge (50% in ~25 minutes) is respectable and close enough in the half-charge stakes, but the Flow's full-charge speed changes behaviour: you stop planning around the battery.
Both are sealed, both are on the standard 18–24-month degradation clock, and neither has an answer to a cheap swappable 18650. If that sentence bothers you, you're a V3 Pro buyer and there's a whole article for you. Both do the 3-minute auto-shutoff dance — you'll wake either device once or twice per bowl. It's a PAX thing. You'll get used to it. Winner: Flow.
Ease of Use
PAX 4: 9.5/10 · PAX Flow: 8.5/10 — PAX 4.
The PAX 4 is the most foolproof device in its bracket, full stop. One button, four modes, haptics, lip-sensing, motion standby, ~20-second heat-up. You don't learn it, you just use it. The real-time manual nudge means the four presets aren't a cage — I used it to sit the device on the benchmark temps for the strain test, which the Flow simply cannot do.
The Flow is nearly as simple but carries small frictions: five modes including a hidden one (Bong Mode is 10–13 clicks of cycling — good luck explaining that in a pub), a slower heat-up, and the quirk that you can't blow the ABV out through the mouthpiece — you scrape it with the multi-tool. None of it is hard. All of it is more than the PAX 4 asks of you. Winner: PAX 4, comfortably.
Cleaning & Maintenance
Both 8.5/10 — a genuine draw.
The two best cleaning experiences PAX has ever shipped, achieved differently. The Flow's side door opens the whole chamber and vapour path to daylight; the PAX 4's magnetic mouthpiece, pop-out 3D screen and accessible airpath do the same job through the top. Both run roughly ten minutes for a proper clean.
The rhythm differs slightly: the PAX 4 wants attention more often (flavour goes "PAX-y" within 5–7 bowls if you skip it), the Flow stretches to 15–20 bowls between proper cleans. High-frequency-low-effort either way. Coming from a Crafty+ cooling unit, both feel like a holiday; coming from a glass Arizer, both are still faff. Winner: dead heat. Buy the PAX cleaning kit whichever you choose and stop improvising with stationery.
Portability
Both 9.5/10 — and both are why people still buy PAX.
The field tests were practically the same experiment in two postcodes. The Flow came to a Manchester gig — Discreet Mode at the bar during the support act, four minutes, zero visible vapour, nobody clocked it. The PAX 4 did a Friday in the Northern Quarter — front jeans pocket, used twice, read as a phone or an MP3 player both times. Identical result: invisible.
The measurable gap: the PAX 4 is ten grams lighter, a shade slimmer, and marginally the better disappearing act in tight jeans. The Flow counters with Discreet Mode at a lower floor (180°C vs the PAX 4's 190°C Stealth) — slightly less visible vapour when it matters most. Winner: PAX 4 by ten grams, which is to say: not a reason to choose either.
Value for Money
PAX 4: 7/10 · PAX Flow: 6.5/10 — PAX 4, and this is the real decider.
The PAX tax runs through both, but it compounds differently. At its price the PAX 4 competes with the V3 Pro and Solo 2 MAX — it loses those spreadsheet fights and I said so, but the markup buys design, ease and portability that at least have no direct substitute at the price.
At its price the Flow competes with the Mighty+ — near enough the same money for meaningfully better extraction. That's a brutal neighbour to live next to, and it's why the Flow's value score is the lowest number in either review. The Flow's defence is real (nothing else combines genuine stealth with 8.5/10 vapour; the Mighty+ looks like a medical pager), but it's a defence, not a win.
Here's the intra-family maths: the price gap buys you 0.7 of a vapour point, Bong Mode, a faster full charge and a side door. It costs you ten grams, ten-ish seconds of heat-up, the included half-pack lid, the manual temperature nudge and the extra registration year on the warranty (the Flow's extended cover is US-only; the PAX 4 does 2+1 here). Winner: PAX 4.
Score Comparison
| Category | PAX 4 | PAX Flow |
|---|---|---|
| Vapour Quality | 7.8/10 | 8.5/10 |
| Design & Build | 9.5/10 | 9/10 |
| Battery & Charging | 7.5/10 | 8/10 |
| Ease of Use | 9.5/10 | 8.5/10 |
| Cleaning & Maintenance | 8.5/10 | 8.5/10 |
| Portability | 9.5/10 | 9.5/10 |
| Value for Money | 7/10 | 6.5/10 |
| Overall | 8.3/10 | 8.3/10 |
Three category wins for the PAX 4, two for the Flow, two dead heats, same overall. I wrote in the PAX 4 review that these two earn the same 8.3 for different reasons — the Flow with hybrid power, the PAX 4 with simplicity and design — and the table above is that sentence with numbers on.
Who Should Buy Which
Buy the PAX 4 if you're most people. If you're buying your first PAX, your only PAX, or replacing a PAX 3 you tolerated for years, this is the one. It's cheaper, lighter, faster to warm, easier to run, and the vapour — while a step behind the Flow — is finally good enough that you never have to apologise for it. It's also the better fit for solo users (that included half-pack lid does real work) and for anyone who wants to nudge temperatures rather than accept five presets. The Golf. You will not regret it, and you'll stop thinking about it within a week, which is the point.
Buy the Flow if vapour is the reason you're hesitating on PAX at all. If you've read a PAX review, nodded along to the design paragraphs, and then gone quiet at "conduction-leaning" — the Flow is PAX's answer to you specifically. It's the only device in the catalogue where the draw genuinely satisfies a Mighty+ owner, and Bong Mode makes it the only PAX with a real water-piece story. You're paying a Mighty+-sized price for that, in a bracket where the Mighty+ exists. Go in with your eyes open.
Buy neither if you're optimising vapour per pound — the Veazy undercuts the Flow comfortably, and the maths only gets crueller from there. That's not a PAX-hater's take; it's in both reviews.
How I Actually Choose
Both live in the going-out rotation, and canonically they split it: the Flow when I want stronger vapour, the PAX 4 when I want lighter pockets. In practice that means the Flow gets the destination nights — gigs, weekends away, anywhere I know I'll want the bowl to actually deliver — running four or five bowls a week at its peak and muscling in on the slot the Crafty+ used to own. The PAX 4 gets the incidental nights: pub, dinner, cinema, three or four sessions a week, front jeans pocket, forgotten until wanted.
When I told Dave both had scored 8.3, he texted back: "Then get neither, buy a Mighty." Which is the most Dave sentence ever committed to a phone, and wrong in exactly the way this article exists to explain — the Mighty+ has never once fit in my jeans.
If the flat caught fire and I could grab one: the PAX 4. Not because it's better. Because it's the one I'd actually replace at full price.
The Verdict (The Bookend)
Nobody needs a GTI. That's the thing about hot hatches — the standard car does the actual job, the school run and the big shop and the airport drop, for less money and less fuel. The GTI exists because "does the job" isn't the only thing a car is for, and the people who buy one know exactly what they're paying for and would thank you not to show them your spreadsheet.
The PAX 4 is the right PAX for most people. The Flow is the right PAX for the people who already know it is. Same platform. Same badge. Same 8.3. One of them is tuned, and tuning has never once been free.
If you're still torn, ask the only question that separates them: when you imagine Friday night, do you picture the pocket or the draw? Pocket: PAX 4. Draw: Flow.
I own a Smeg toaster argument and a Take That comeback, and it turns out they get along fine in the same drawer.
FAQ
PAX 4 vs PAX Flow — which should I buy?
The PAX 4, unless vapour strength is specifically why you're hesitating. Both score 8.3/10, but the PAX 4 is cheaper, lighter, faster to heat, and easier to live with. The Flow's 8.5/10 vapour (vs 7.8) and Bong Mode are the only two reasons to pay the extra — good reasons, but only if they're your reasons.
Is the Flow's vapour really that much better?
Noticeably, yes. The redesigned chamber and hybrid heating put it in Veazy/Crafty+ conversation — territory no PAX had entered before. The PAX 4 runs the same architecture scaled down: the best non-Flow PAX vapour, still conduction-leaning, still a sipper. Side by side on Wedding Cake at mid-temp, both resolve the flavours; the Flow does it with more density behind it.
Can I use either with a bong or water piece?
The Flow is built for it — Bong Mode runs 225°C with the motion sensor disabled, accessed by cycling the four visible modes three times. Fair warning: the grip gets properly hot. The PAX 4 has no dedicated water mode; Mode 4 (220°C) through a water piece works at home, but it's an improvisation, not a feature. If water is a regular part of your sessions, that's a genuine point for the Flow.
Which has the better battery?
Split decision. The PAX 4 carries the bigger cell (2800 vs 2000mAh) for roughly similar endurance — about five sessions against four to six. The Flow charges much faster: 50% in 20 minutes, full in under 40, against the PAX 4's ~100-minute full charge. Both are sealed, both face the 18–24-month degradation timeline, neither battery is user-replaceable.
What about cleaning — is one easier?
They tie at 8.5/10 and they're the two best cleaning experiences PAX has shipped. The Flow opens via the side door; the PAX 4 via the magnetic mouthpiece and pop-out 3D screen. About ten minutes each for a proper clean. The PAX 4 wants attention slightly more often; the Flow stretches longer between cleans.
Do the warranties differ?
Yes, and it's underreported. The PAX 4 gets 2 years, extendable to 3 if you register within 30 days. The Flow gets 2 years standard in the UK — the 4-year extended registration cover you'll see advertised applies only in eligible US regions. Neither covers battery degradation.
Is either one good with concentrates?
No. Both are dry-herb only, no inserts available or planned. Different device category entirely if concentrates are your primary use.
About Dennis M.
Dennis M. has been vaping daily for the best part of a decade — since an original Mighty in 2018 — and has tested 50+ devices for this site. He works in IT, has ADHD, and uses cannabis for chronic pain management. He lives in Manchester with his partner Sarah, who has watched him carry two nearly identical aluminium pebbles out the door on alternate Fridays for six weeks and has, with visible restraint, said nothing.
He is aware that owning both the hatchback and the hot hatch defeats the purpose of the metaphor. He has decided the metaphor can cope.
A note on spelling: 'vaporizer' is the de facto international spelling, but I've stuck with the British 'vaporiser' throughout this blog.
Questions, corrections, or a device you want tested? dennis@herbvape.co.uk
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Full Reviews:
Head-to-Head Comparisons:
- PAX 4 vs PAX Mini 2: The Clutch Bag and the Handbag
- PAX 4 vs V3 Pro: Design Tax vs Spec Sheet
- Legacy Pro 2 vs PAX Flow: Two Premium Hybrids Compared
Best-Of Guides:
New to Vaping?
Get Both at HerbVape.co.uk
PAX 4 — the hatchback: lighter, simpler, kinder on the wallet.
Buy the PAX 4 →
Worth grabbing with it: PAX 3D Oven Screen Set — genuine replacement screens for the weekly clean.
PAX Flow — the hot hatch: the strongest vapour PAX makes, plus Bong Mode.
Buy the PAX Flow →
Worth grabbing with it: PAX FLOW Grip Sleeve — silicone sleeve for the warm-grip problem, non-negotiable if you'll use Bong Mode.
Just one more bowl.
Last updated: 25 September 2026.
Review Policy: I buy or borrow the devices I review. HerbVape.co.uk is my employer, but my opinions are my own — they pay me to be honest, not to sell you shite. Affiliate links and discount codes exist because running a site costs money, not because they influence scores.
Strains Used: Jack Herer — sativa (Haze × Northern Lights #5 × Shiva Skunk), ~20% THC, terpinolene/caryophyllene/pinene-dominant, pine-citrus-pepper profile with fragile top notes. Wedding Cake — indica-leaning hybrid (Triangle Kush × Animal Mints, via Triangle Mints #23), ~24% THC, caryophyllene/limonene/myrcene-dominant, vanilla-cream-dough dessert profile over peppery earth. Same two strains, same jars, across every vaporiser reviewed on this site — the strain is the control, the device is the variable. Strain effects vary by individual, batch and consumption method.
Medical & Legal Disclaimer: Nothing in this review constitutes medical advice, and I am not a medical professional. Cannabis is a controlled substance in the UK; medical cannabis is legal only on prescription from a registered specialist clinic — Sapphire, Cantourage and Zerenia are three of the larger ones. HerbVape.co.uk sells vaporiser hardware only: we do not sell, prescribe, or recommend cannabis or cannabis products. Vaporisers are sold for use with legal dry herbs and legally prescribed medical cannabis. You must be 18 or over to buy one, and cannabis law varies by jurisdiction — check yours.