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.
Choose the model, then check the current offer
Use the fit guide, budget shortlist, and Sihoo comparison together. When you know the right lane, move to the live chair deal feed.
Short answer: start with the M18 when budget and manually adjustable lumbar support matter most; consider the M59AS or B100 family when desk clearance is the problem; move to the C300 or C300 Pro when back movement and a broader adjustment set matter more than the lowest price. Compare the exact version across credible UK sellers before you buy.
How we researched this guide: Desworthy has not physically tested these chairs. We compare manufacturer specifications, policy pages, dated UK purchase information, and named independent sources where they cover a model. Manufacturer pages establish features and warranty information. Retailer pages establish a dated purchase route only. Sources were checked on 3 August 2026.
Quick answers about choosing a Sihoo chair
Which Sihoo chair is the best starting point?
There is no single best Sihoo chair for every body and desk. Start with the M18 if budget and manually positioned lumbar support lead the decision, the M59AS or B100 family if the arms must move out of the way, and the Doro C300 range if you are paying for more back movement and adjustment. Measure first, then narrow the model list.
Does the standard Doro C300 have adjustable seat depth?
Do not assume it does from a pair of depth figures or from another C300 version. The C300 Pro and Pro V2 publish clearer seat-depth controls; for the standard C300, ask the retailer to confirm the exact selected version when a sliding seat is essential.
Should the largest discount decide which chair to buy?
No. A discount can improve the price, but it cannot correct a seat that is too deep, arms that hit the desk, or a return policy that makes a fit problem expensive. Choose the chair first and compare current offers second.
Choose by value and fit, not by one temporary price
| Model | Best comparison role | Published advantage | What to verify before buying |
|---|---|---|---|
| M18 | Budget adjustment option | Lumbar height and depth adjustment, height-adjustable arms, and a headrest. | Fixed 17.91-inch seat depth and incomplete published UK seat-height information. |
| M59AS | Compact-desk option | Flip-up arms, 3D arm adjustment, and a stated 17.13-inch seat depth. | Whether the published width and return terms work for your body and room. |
| B100 and B100 Pro | Flip-up-arm alternative | Flip-up arms and recline positions; the Pro adds more arm and headrest adjustment. | Missing complete seat dimensions on the UK pages. |
| M57 | Simpler full-mesh option | Full mesh, manual lumbar adjustment, and 3D arms. | Fixed 18.11-inch seat depth. |
| Doro C300 | Feature-led upgrade | Flexible back, self-adaptive lumbar design, coordinated arms, and weight-sensing recline. | The exact version, selected-variant price, stock signal, and whether it has the seat-depth control you need. |
| Doro C300 Pro | Adjustment-led upgrade | Published adjustable seat depth, backrest-height adjustment, and 6D linked arms. | Whether its higher street price buys controls you will actually use. |
| Doro C300 Pro V2 | Wider adjustment range | Published 16.9 to 18.5-inch seat-depth range and 8D arms. | Whether the extra controls justify the price difference from the C300 Pro. |
| Doro S300 | Premium recline-focused option | Free-floating recline, dynamic lumbar support, and adjustable seat depth. | Conflicting capacity information and the need for hands-on comfort evidence. |
These roles describe trade-offs. They are not universal winners, and no capacity rating proves that a seat will fit a particular body.
M18: choose it when value means useful basic adjustment
The M18 is the first Sihoo model to compare when you want manually positioned lumbar support without moving into the Doro price range. Its published feature set includes lumbar adjustment in height and depth, height-adjustable arms, a pivoting headrest, tilt tension, and recline up to 126 degrees.
The price advantage does not remove the need to measure. The fixed 17.91-inch seat depth may be too long for some users, and the UK page does not give a complete seat-height range. Creative Bloq has published a hands-on M18 review; we link it as an external test, not as Desworthy testing.
M59AS and B100: choose them when the desk needs to disappear
Flip-up arms can be more useful than extra armrest directions when the chair must slide under a compact desk. The M59AS lists 3D flip-up arms and a 17.13-inch seat depth. The B100 family also uses flip-up arms, while the Pro version adds more headrest and arm adjustment.
The limitation is missing fit data. The UK product pages do not publish every seat measurement needed for a reliable body-fit comparison. Treat that as a reason to confirm dimensions and return conditions before ordering, not as a reason to guess from an overall chair size.
M57: choose it for a simpler full-mesh layout
The M57 uses a conventional full-mesh design with manual lumbar adjustment, 3D arms, and recline up to 126 degrees. Its stated 18.11-inch fixed seat depth is the decisive measurement. It can be a sensible fit for a buyer whose thigh measurement suits it, but it is not a substitute for an adjustable seat pan.
C300 and C300 Pro: pay for a clearer adjustment case
The standard C300 is about the flexible back, adaptive lumbar design, coordinated arms, and a weight-sensing recline mechanism. The C300 Pro makes a clearer case when you specifically need published adjustable seat depth, backrest-height adjustment, and 6D linked arms. The Pro V2 expands the published seat-depth range and arm adjustment further.
Choose based on the control you will use. A complex chair is not automatically better if your desk, body, and work pattern do not require the extra range. For the basic C300, ask the retailer to confirm the exact selected version before assuming that a listed depth range means a sliding seat.
S300: treat the premium option with more caution
The S300 has the most ambitious recline-led feature set in this guide, including free-floating recline, dynamic lumbar support, and adjustable seat depth. It is also the model where specifications leave the most unanswered questions about mesh pressure, lumbar firmness, control feel, and long-term durability. Sihoo’s published capacity information has conflicted across pages, so buyers near the stated limit should request written confirmation.
Check more than the Sihoo store before paying
Sihoo is sold through more than its own store, including marketplace and retailer channels. Compare each source, but only treat a listing as like-for-like when the model, colour, version, seller, fulfilment route, delivery cost, return terms, and UK warranty coverage match. A marketplace price without those details is a lead to investigate, not proof of better value.
Current direct pages are linked in the table. We will add a second retailer link only after the exact model and after-sales route are verified. This is more useful than sending readers to a generic marketplace result or a grey-import listing.
Sources
- Sihoo UK premium ergonomic office-chair collection
- Before ordering, review the current Sihoo return and warranty terms on the official site.
- Creative Bloq hands-on Sihoo M18 review
- OSHA chair evaluation checklist
- Individual Sihoo product pages linked in the comparison table above