Desworthy Editorial Team
Desworthy editorial reviewer focused on ergonomic chair research, desk tech, affiliate disclosure, and practical UK home office buying decisions.
Last reviewed on by Desworthy Editorial Team.
Source information was checked on 7 October 2026. The editorial update date above does not mean prices, availability or retailer terms were checked again. Confirm those details with the retailer before buying.
Choose the M18 if you want a cushioned seat and the lowest current Sihoo entry price. Choose the M57 if you specifically want a mesh seat and armrests that also move forwards, backwards and sideways through rotation. The upgrade is about those two changes. A larger model number does not establish a better fit.
- White M18 versus Light Grey M57: £159.99 versus £199.99, a £40 difference.
- Black versus Black: £169.99 versus £229.99, a £60 difference.
- Both list manually adjustable lumbar support and a maximum 126° recline. Spending more does not buy a larger published recline angle here.
Last verified: 7 October 2026. Prices are UK direct-store listings before a separately applied code, for the colours named below.
Compare the seats before counting the controls
| Buying question | M18 | M57 | What follows from the difference |
|---|---|---|---|
| What supports your thighs? | Cushioned, W-shaped seat; mesh back | Mesh seat and back | Start with M18 if you want padding; start with M57 if a mesh seat is a requirement |
| How do the arms adjust? | Height adjustment | 3D adjustment: height, depth and rotation | M57 gives you more ways to position the pads around a keyboard or mouse |
| Can you position the lumbar support? | Manual height and depth adjustment | Manual height and depth adjustment | This is not a change from manual to adaptive lumbar support |
| Published maximum recline | 126° | 126° | The M57 premium needs another justification |
| Lowest available colour checked | White, £159.99 | Light Grey, £199.99 | £40 more for the selected M57 |
| Black colour checked | £169.99 | £229.99 | £60 more when both chairs are Black |
Feature and price sources: M18 UK product page and M57 UK product page.
If your current chair’s arm pads sit too far behind your elbows, the M57’s extra movement is a useful reason to upgrade. If height is the only arm adjustment you use, the M18 already supplies that control. In that case, decide whether you actually want to sit on mesh before paying the difference.
Mesh and padding are preferences as well as construction choices. Neither product page provides a comparable measured cooling result, pressure map or long-term sag test. Calling one seat “30% cooler” or more durable would add a number the sources do not establish.
Two straightforward ways to choose
Choose M18 for a spare room or a first desk setup when a cushioned seat suits you and its arms can meet your elbows without lifting your shoulders. Keep the price difference available for a footrest, delivery or another part of the workstation that needs adjustment.
Choose M57 for a mesh-seat workstation when you want that seat construction and can make use of the moving arm pads. Check the pads in your typing position, then in your mouse position. Being able to move them is useful only if the resulting positions work with the desk.
The HSE workstation checklist puts the chair within the whole workstation: supported feet, a usable backrest and a comfortable working position matter together. A chair cannot solve a desk-height problem simply by having more adjustment directions.
For buyers already considering M57 Black, read the C300 versus M57 comparison. The current £20 difference between those Black standard listings creates a separate question about manual versus moving lumbar support.
Questions worth settling before ordering
Is the M57 always £40 more expensive?
No. The £40 comparison uses M18 White and M57 Light Grey. The Black-to-Black difference was £60 on the verification date. Colour selection changes this comparison even without a discount code.
Does the M57 have a mesh seat, or just a mesh back?
The UK page describes a mesh seat and back. The M18 has a cushioned seat and mesh back. That is the main seat-construction difference to check when comparing photographs or retailer listings.
Which is the safer choice for a shorter user?
Neither can be selected safely from the price alone. Obtain the exact seat-height and usable-depth measurements you need, then compare them with your supported sitting position. If your feet cannot reach a stable support, resolve that fit problem before choosing either chair.
Does M57 add automatic lumbar adjustment?
No. Both pages describe manual lumbar positioning. The C300 range is the relevant comparison when you want a lumbar section designed to follow movement.
Are returns free if I dislike the seat?
Do not assume so. Sihoo’s main return policy describes free returns for damaged, defective or wrong items. Its after-sales policy assigns non-defect return shipping to the buyer. Ask for the applicable process and cost before assembly.
Sources and price notes
Sources were checked on 7 October 2026. The product pages establish the listed construction, controls and prices; HSE supplies the workstation checklist. The £40 and £60 gaps are Desworthy calculations using the named colour prices. They exclude delivery, return costs and any unconfirmed code saving.
Current purchase routes: M18 White offer and M57 Light Grey offer. Recheck the selected colour and final payable total at the retailer.
Image credit: Sihoo, product photograph.
Note: This article is for reference only.