There is a decision buried in the Aeron order form that most buyers never realise they are making, and a second version of it waiting for anyone shopping the used market. Herman Miller does not sell one Aeron back. It sells four different back-support configurations on the same chair, they look broadly similar in a photograph, and they behave quite differently against your lower back.
This guide sets out what each one is, in Herman Miller's own published words, what the company actually publishes a measurement for and what it does not, how to tell which support is fitted to a chair in front of you, and what we hold in Australia. If you are still deciding whether the Aeron is the right chair at all, start with our full Aeron review — this page assumes you have already landed on an Aeron and are working out which back you want.
The four back supports Herman Miller actually lists
Herman Miller's Aeron product sheet lists the back-support choices as no additional support, PostureFit, Adjustable Lumbar Support and Adjustable PostureFit SL Support, with the last three marked "Optional". The company's own store configurator describes them like this, verbatim:
| Option, as Herman Miller names it | Herman Miller's own description | Published adjustment range |
|---|---|---|
| Basic Back Support | "Zonal Back Support is provided by the 8Z Pellicle material in the backrest." | Nothing to adjust — there is no pad |
| PostureFit | "Adjusts to support your natural spinal alignment by stabilizing your sacral region." | None published |
| Adjustable Lumbar Support | "Adjusts to support the natural curve of the lumbar region of your spine. Lumbar support can be adjusted vertically over a 4.5-inch range." | 4.5 in / 114 mm vertical |
| Adjustable PostureFit SL | "Two individual pads flex independently; the top pad supports your lumbar, the bottom stabilizes your sacrum. System can be adjusted to fit the curve of your spine." | None published |
That table is the whole argument in miniature, and the third column is the part worth sitting with. Herman Miller publishes a hard number for exactly one of the four — the lumbar pad's 4.5 inch travel, which is 114 mm. For PostureFit and for PostureFit SL it publishes descriptions of what the pads do and no measurement of how far they move. We are not going to invent one. If a figure for PostureFit SL travel turns up in a listing or a forum post, it did not come from Herman Miller, and you should treat it the way you would treat any other number nobody will put their name to.
Adjustable Lumbar Support: one pad, one axis, and a number you can check
The Adjustable Lumbar Support is the simpler of the two. It is a single curved pad that sits in a track behind the mesh and slides up and down. You set its height, and that is the entire adjustment. Herman Miller's own user adjustment guide tells you to do it like this: "Using equal pressure on each end of the lumbar support, raise or lower it to desired position within adjustment track. Adjust pad height so that it comfortably supports the natural curve of your spine."
Two hands, even pressure, one axis. It is the oldest of the current options and by some distance the easiest to explain to somebody who has never set up an office chair before. The 114 mm of travel is generous — enough to move the pad from well down on the pelvis up into the middle of the lower back — and because it is a published figure you can measure it against the chair and know whether the part is working properly.
Where it stops short is that it does one job in one place. The pad pushes the mesh forward at whatever height you leave it at, and nothing else on the back of the chair changes. If the shape you want is "firm here, softer there", the single pad cannot give you that, because there is only one pad.
Adjustable Lumbar Support suits you if
- You want a chair you can set once and forget, with one control and no interaction between adjustments.
- You already know roughly where you like support in your lower back and you want to put a pad exactly there.
- You are buying used, the chair in front of you has a lumbar pad, and it is otherwise the right size and in good condition. A working lumbar pad is not a reason to walk away from an otherwise good chair.
- You share the chair with other people and want an adjustment anyone can understand in five seconds.
Adjustable Lumbar Support does not suit you if
- You want the chair to do something different at the base of your pelvis from what it does higher up. One pad cannot be in two places.
- You have tried lumbar pads before and found that wherever you put them, they end up either too low to notice or high enough to feel like a knuckle. Moving to a two-pad system is a real change, not a marketing one.
PostureFit SL: two pads, two heights, and the reason it exists
PostureFit SL is the one most people mean when they say "the good one", and it helps to know where it came from. Herman Miller's own Aeron design history records that the company "introduces its patented PostureFit technology, in collaboration with Dr Brock Walker, back care specialist, designer, and holder of multiple patents in fields including biomechanics and ergonomics" in 2002, and that in 2016 the "Aeron Remastered debuted a more refined tilt mechanism, adjustable PostureFit SL, and an updated Pellicle called 8Z which incorporates eight separate 'tensioned' zones — four in the seat, four in the back".
So PostureFit came first, in 2002, and it addressed one region: the sacrum, the wedge of bone at the very base of the spine. PostureFit SL came fourteen years later and added a second pad above it. The "SL" is doing real work in that name — sacral and lumbar. Herman Miller's description is that the system has "two individual pads" that "flex independently", with "the top pad supports your lumbar, the bottom stabilizes your sacrum".
The practical difference is that you are no longer choosing one height for one pad. You are setting two supports that sit at different heights and can be set to different depths, so the back of the chair can push more firmly in one place than the other. That is a genuinely different thing from a single sliding pad, and it is the reason the SL specification carries a price premium wherever it is sold.
Herman Miller's user adjustment guide sets it up in a specific order, and this is the part almost nobody does: "adjust PostureFit SL so that it comfortably supports the natural alignment of your spine and provides lower back comfort" — but only after engaging the tilt limiter forward and getting your back properly into the pocket of the chair back. Setting the pads while you are perched on the front of the seat, which is how most people do it, sets them against a position you are not going to sit in.
We should be straight about one thing. Herman Miller's marketing copy for PostureFit SL says it "activates a healthful posture and helps reduce muscle fatigue". That is the manufacturer's claim, not ours, and we are not going to repeat it as a finding. What we will say is what is checkable: there are two pads instead of one, they move independently, and they are at different heights. Whether that feels better to you than a single pad is a question a ten-minute sit answers better than any paragraph.
PostureFit SL suits you if
- You sit for long stretches and tend to slide forward on the seat as the afternoon goes on. Support at the sacrum is the part of the chair that is doing something about where your pelvis ends up.
- You have found single-pad lumbar supports either too vague or too pointed, and you want to separate "hold my pelvis" from "support my lower back".
- You are prepared to spend ten minutes setting the chair up properly once, following Herman Miller's order of operations rather than poking at it while perched on the front edge.
- You are buying new and the price difference is not the deciding factor — it rarely is at this level of chair.
PostureFit SL does not suit you if
- You want the fewest possible controls. Two pads is two more things to get wrong, and a badly set SL is worse than a well-set lumbar pad.
- You are buying secondhand on price and the SL chairs in front of you are in visibly worse condition than the lumbar-pad ones. Condition beats specification on a used chair every time.
- Your actual problem is that the chair is the wrong size. No back support rescues a size C under a 165 cm person, and none of them changes the Aeron's fixed seat depth.
The two you will mostly meet secondhand
Basic Back Support and the original PostureFit are still out there in large numbers, and if you are shopping used in Australia you will meet both.
Basic Back Support is exactly what it sounds like: no pad at all, with the support coming from the tensioned mesh itself. Herman Miller's wording is that "Zonal Back Support is provided by the 8Z Pellicle material in the backrest". Plenty of people sit happily in one. It is the configuration that most often shows up in a listing photographed from the front, because from the front you cannot tell.
PostureFit, without the SL, is the 2002 original: one pad, low down, aimed at the sacrum rather than the lumbar curve. Herman Miller describes it as adjusting "to support your natural spinal alignment by stabilizing your sacral region". It is not the same thing as the Adjustable Lumbar Support even though both are single pads — they sit at different heights and are aimed at different parts of you.
How to tell which one a chair has, from a listing
This is the practical skill, and it takes about five seconds once you know what you are looking at.
- Ask for a photograph of the back of the chair. Every one of these differences is visible from behind and invisible from the front. A seller who will not photograph the back of the chair is telling you something.
- Nothing behind the mesh at all — Basic Back Support.
- One pad, sitting low, close to where the back meets the seat — PostureFit.
- One pad on a visible vertical track, higher up the back — Adjustable Lumbar Support.
- Two pads, one above the other — PostureFit SL.
Two things that trip people up. First, "lumbar support" in a listing title means nothing on its own; three of the four configurations can be described that way by a seller who is not being careful. Second, the back support tells you nothing about size, and size is the decision that actually matters on an Aeron — see our Aeron size guide before you fall in love with a chair because it has the right pads.
Head to head
| Adjustable Lumbar Support | Adjustable PostureFit SL | |
|---|---|---|
| Number of pads | One | Two, flexing independently |
| Region Herman Miller names | Lumbar | Lumbar (top pad) and sacrum (bottom pad) |
| Adjustment | Height, within a track | Set to fit the curve of the spine; both pads |
| Range Herman Miller publishes | 4.5 in / 114 mm vertical | Not published |
| Introduced | Long-standing option | 2016, with the Aeron Remastered |
| Set-up time | Seconds | Ten minutes, done properly |
| Easy to get wrong | Hard to get badly wrong | Easy to get wrong if set while perched forward |
| What we stock in Australia | Not held | Every Aeron on our floor |
What it costs in Australia, and what we actually hold
Every Herman Miller Aeron we stock is the PostureFit SL specification. That is a deliberate choice rather than an accident of supply: if we are going to hold one configuration of a chair this size, it is the one with the most adjustment in it, because a buyer can always leave an adjustment alone and nobody can add one that is not there.
Live selling prices, checked on the day this was published:
| Finish and base | Sizes held | Price |
|---|---|---|
| Graphite, graphite base | A, B, C | $2,150 |
| Mineral, satin aluminium base | B, C | $2,330 |
| Onyx, graphite base | B, C | $2,340 |
| Onyx, polished aluminium base | B, C | $2,630 |
| Mineral, polished aluminium base | B, C | $2,640 |
A note on sizes: the smaller Aerons move quickly and size A is the one we hold in the smallest numbers at any given moment. If you have read the size guide and concluded you want an A, ring us on 02 9640 0642 rather than assuming there is one on the shelf. The colour and base choices above are all size B and C except for the Graphite, which we hold in all three.
If you want a plain lumbar pad rather than PostureFit SL, tell us. There is no configuration of this chair we cannot talk to you about, and it is a five-minute phone call rather than a guess made from a web page.
Everything here is genuine Herman Miller product, brand new, supplied as an international parallel import — which describes the supply route, not the product. The cover is our own 12-year Chair Dinkum warranty rather than Herman Miller's, and it is handled here in Sydney. The full position is set out in Herman Miller in Australia: what parallel import actually means, and who warrants your chair. Your Australian Consumer Law rights apply in addition and cannot be excluded.
What the back support cannot fix
This is the part a shop floor tells you and a product page does not. The back support is the last adjustment you should be worrying about, because three things sit above it and no pad compensates for getting them wrong.
Size. The Aeron's seat depth is fixed by the size you buy — 406 mm on a size A, 432 mm on a size B, 470 mm on a size C. There is no seat depth adjustment on any Aeron, in any configuration, at any price. Herman Miller recommends size B for anyone falling between sizes. If the seat is too long for your thigh, a second pad in the small of your back is not the answer; a different size is.
Seat height. Herman Miller publishes 366–490 mm for a size A, 376–579 mm for a size B and 401–579 mm for a size C. That 579 mm ceiling is the reason the Aeron is not a standing-desk chair. If you work standing for part of the day, the chair you want is a saddle — the HÅG Capisco 8106 goes far higher, and our Capisco buying guide explains which gas lift you need for it.
Tilt. Herman Miller's adjustment guide is blunt that the tilt limiter comes first: "Rotate knob forward to limit recline to preferred position", and "Engage the tilt limiter when you want to sit in an upright or partially reclined position." Set the recline you want, then set the pads against it. Doing it the other way round is how people end up convinced the chair does not fit them.
If the Aeron is not the chair
Being honest about what a chair does means being honest about who should be looking at a different one on our floor.
If the fixed seat depth is the problem, the chair to look at is the HÅG SoFi Mesh. Flokk publishes an adjustable seat depth of 38–46 cm on it, against the Aeron's fixed figure, and it starts at $750 without arms and $950 with the SlideBack armrests. It is certified EN 1335 Class A. It is not a mesh-seat chair — only the back is mesh — and it is a very different proposition from an Aeron, but for a shorter or longer thigh it does something the Aeron structurally cannot.
If you want a Herman Miller with adjustable seat depth, that is the Mirra 2, which is the only one of the four Herman Miller chairs with it. Worth knowing that the Mirra 2 splits its back support the same way the Aeron does: sacral PostureFit support is standard on it, and the height-adjustable lumbar is a separate option, so the same "which back" question applies there too. Our Mirra 2 sells on backorder rather than from Sydney stock, so ask us about timing before you commit. Our Mirra 2 review sets out the rest.
If you cannot settle, sit in them. Our Pyrmont showroom has them side by side by appointment, and ten minutes in a chair settles arguments that ten thousand words cannot. Browse the full range at Herman Miller Australia.
The recommendation
For a chair you are buying new and keeping for a decade, take PostureFit SL. Not because of anything anybody claims it does to your spine, but because it is the configuration with the most adjustment in it, and adjustment you do not use costs you nothing while adjustment you do not have costs you the chair. That is why every Aeron we hold is the SL specification.
For a chair you are buying used, buy on condition and size first and take whatever back support comes with it. A tidy size B with a plain lumbar pad is a far better purchase than a tired one with PostureFit SL, and the pad is not the part that wears out.
And if what you actually need is a chair that goes to standing height or has an adjustable seat depth, neither back support is the answer and the Aeron is the wrong chair. Say so on the phone and we will point you at the right one.
Frequently asked questions
What is the difference between PostureFit and PostureFit SL?
PostureFit, introduced in 2002, is a single pad aimed at the sacral region at the base of the spine. PostureFit SL, introduced with the Aeron Remastered in 2016, adds a second pad above it: Herman Miller describes two individual pads that flex independently, with the top pad supporting the lumbar region and the bottom stabilising the sacrum. The SL in the name stands for sacral and lumbar.
How far does the Aeron lumbar support move?
Herman Miller publishes a 4.5 inch vertical range for the Adjustable Lumbar Support, which is 114 mm. It is the only one of the four back-support options for which Herman Miller publishes an adjustment measurement. For PostureFit and for PostureFit SL the company describes what the pads do but publishes no range, and we do not state one.
Which Aeron back support does Chair Dinkum stock?
Every Herman Miller Aeron we stock is the PostureFit SL specification. That is deliberate: it is the configuration with the most adjustment in it, and a buyer can always leave an adjustment alone, whereas nobody can add one that is not there. If you want a different configuration, ring us on 02 9640 0642 and we will talk it through.
Can I tell which back support a used Aeron has from the photos?
Only from a photograph of the back of the chair. Nothing behind the mesh means Basic Back Support; one pad sitting low near where the back meets the seat is PostureFit; one pad on a visible vertical track higher up is Adjustable Lumbar Support; two pads, one above the other, is PostureFit SL. From the front all four look the same, and the phrase "lumbar support" in a listing title can describe three of them.
How do I set up PostureFit SL properly?
Herman Miller's user adjustment guide sets the order: engage the tilt limiter forward and get your back properly into the pocket of the chair back first, then adjust PostureFit SL so that it comfortably supports the natural alignment of your spine and provides lower back comfort. Setting the pads while perched on the front of the seat sets them against a position you are not going to sit in, which is the most common reason people conclude the chair does not fit them.
Does a better back support fix a chair that is the wrong size?
No. The Aeron's seat depth is fixed by the size you buy — 406 mm on a size A, 432 mm on a size B, 470 mm on a size C — and there is no seat depth adjustment on any Aeron in any configuration. If the seat is too long for your thigh, a different size is the answer, not a different pad.
Is the Aeron any good at a standing desk?
No. Herman Miller publishes seat height ranges of 366–490 mm for a size A, 376–579 mm for a size B and 401–579 mm for a size C, so the chair tops out at 579 mm. If you work standing for part of the day, a saddle chair such as the HÅG Capisco 8106 goes far higher and is the right tool for it.
Can PostureFit SL be retrofitted to an older Aeron?
We do not publish an answer to that, because Herman Miller does not publish one we can point you to. Parts availability and fit vary by chair age and configuration, so bring us the chair or its details and we will tell you what we find rather than guessing. Ring 02 9640 0642.
Sources
- Herman Miller, Aeron Chairs product sheet (hermanmiller.com product literature) — the four back-support options and the "Optional" designations.
- Herman Miller Store, Aeron Chair configurator and Aeron Chair buying guide — the verbatim option descriptions and the 4.5 inch lumbar range.
- Herman Miller, Aeron Chairs user adjustment guide (hermanmiller.com user information) — the PostureFit SL, lumbar height, tilt limiter and forward tilt instructions.
- Herman Miller, Aeron design story (hermanmiller.com) — PostureFit in 2002 with Dr Brock Walker, and adjustable PostureFit SL with the 2016 Remastered.
- Herman Miller published Aeron specifications and the Aeron size and fit reference — seat depths and seat height ranges by size.
- Flokk, HÅG SoFi Collection factsheet 2025 — the SoFi's adjustable seat depth.
- Prices and stock checked live against chairdinkum.com.au on 15 September 2026.
