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 M57 if you want to position the lumbar pad yourself. Choose the standard C300 if you prefer its lumbar section to follow movement and want coordinated armrests. With the current Black standard listings only £20 apart, the support design matters more than a vague distinction between “budget” and “premium”.
- M57 Black: £229.99. C300 Black Standard: £249.99. Difference: £20.
- M57 Light Grey: £199.99. Compared with C300 Black Standard, the saving is £50.
- Both use a mesh seat and back. Changing to C300 does not mean changing from a padded seat to mesh.
Last verified: 7 October 2026. The price gaps use the colours and standard configurations named above, before a separate code.
The controls you will use every day
| Question | M57 | Standard C300 | Practical decision |
|---|---|---|---|
| How is lumbar support positioned? | Manual height and depth adjustment | Self-adaptive dynamic lumbar section | M57 for a setting you deliberately place; C300 for the moving-support layout |
| How do the arms move? | 3D: height, depth and rotation | 4D coordinated arms, moving with recline | Check pad position in typing and reclined postures |
| Seat and back construction | Mesh | Mesh | Choose on fit and controls rather than assuming a material upgrade |
| Maximum listed recline | 126° | 130° | A four-degree published difference does not measure mechanism comfort |
| Current Black standard price | £229.99 | £249.99 | C300 costs £20 more |
| Current lower-priced M57 alternative | Light Grey, £199.99 | Black Standard, £249.99 | £50 gap with different colours |
Sources: M57 UK and standard C300 UK.
Keep the manual control if that is what you like
A moving lumbar section is not automatically preferable to a manual pad. If you already know where you want contact against your lower back and prefer leaving it there, M57 has the more straightforward adjustment case. Set its height and depth, then check that you can sit against the backrest without being pushed forward.
C300 is the more relevant candidate when you change position frequently and want to assess a support section designed to follow those movements. At the current Black price gap, that is an inexpensive step between these listings, but it still needs to feel right at your desk.
The lumbar-control guide compares positioning methods rather than inventing a universal firmness ranking. Manufacturer descriptions establish how a mechanism is intended to work; they do not measure pressure on your particular back.
Seat depth can change the shortlist
The C300 UK page lists a 43.5–46 cm seat-depth range and its FAQ describes adjustment. Other model-comparison material has given different signals about the base C300’s seat control. If a sliding seat is essential, request confirmation for the exact UK version before ordering.
Do not substitute an original C300 Pro or Pro V2 specification for the standard chair. The original Pro comparison and Sihoo lineup guide keep those versions separate. Around the same budget, B300 Pro explicitly describes a 5 cm slide, although its endpoint measurements still deserve checking.
Use the HSE workstation checklist to check supported feet, thigh clearance, back support and working reach. Resolve a seat-height or desk-clearance mismatch before paying for a different lumbar mechanism.
Quick buying questions
Is C300 worth £20 more than M57?
For the current Black listings, it is worth shortlisting if you want the moving lumbar layout and coordinated arms. If you prefer manual positioning, save the £20. The Light Grey M57 creates a larger £50 gap against Black C300.
Does M57 have a padded seat?
No. M57 is described as mesh seat and back. The M18 comparison is the relevant Sihoo choice when a cushioned seat is part of the decision.
Is C300 Pro the same as standard C300?
No. Original C300 Pro, Pro V2 and Ultra V2 have separate specifications and prices. Match the full model name and selected version, especially for seat-depth and armrest claims.
Does the C300 footrest version cost £249.99?
That price refers to Black Standard. Black Footrest was a separate £349.99 listing when checked. A package change should not be hidden inside the model comparison.
Can I return the chair if I dislike the lumbar pressure?
Confirm the change-of-mind process before assembly. The main Sihoo policy and after-sales policy distinguish defects from other returns; non-defect transport is assigned to the buyer and the stated return route includes condition and packaging requirements.
Source and calculation notes
Sources were checked on 7 October 2026. Product features are manufacturer-reported. The £20, £50 and £100 configuration gaps are arithmetic from the specified UK listings, excluding delivery and any unconfirmed code. They are not comfort scores.
Current offer details: M57 Light Grey and C300 Standard.
Image credit: Sihoo, product photograph.
Note: This article is for reference only.