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 B300 Pro if its documented 42–47 cm seat-depth range and 6D arms meet your requirements. Choose the standard C300 if you prefer its support layout and slightly wider published seat, and can confirm the controls on the exact UK version. Both describe moving lumbar support. “Pro” in the B300 name does not make it part of the C300 Pro family.
The available B300 Pro White Standard listing was £239.99. C300 Black Standard was £249.99, while C300 White Standard was £269.99. That creates a £10 gap across the first two colours and a £30 gap when both selected chairs are White.
Last verified: 7 October 2026. These are standard chair prices before a separate code; footrest configurations are different listings.
Buy the adjustment you actually need
| Requirement | B300 Pro | Standard C300 | Better starting point |
|---|---|---|---|
| A clearly documented seat slide | 42–47 cm; UK page explicitly describes 5 cm adjustment | UK table lists 43.5–46 cm; confirm the actual slider/control for the selected version | B300 Pro when its published 42 cm minimum suits your thigh clearance |
| Lumbar design | Dynamic 4D MicroFit system | Self-adaptive dynamic lumbar section | Compare the contact and movement of each layout |
| Armrest category | 6D | 4D coordinated | Compare usable pad positions; the direction count alone cannot establish comfort |
| Backrest-height control | 5.5 cm adjustment stated | Adjustable backrest described | Check the usable support position against seated torso length |
| Published seat width | 48.5 cm | 49.5 cm | C300 lists 1 cm more seat width; arm spacing is separate |
| Published maximum load | 120 kg | 136 kg | Exclude a chair if your intended load exceeds its stated limit |
| Published maximum recline | 135° | 130° | B300 Pro has the larger stated angle; mechanism feel remains a separate question |
| Available White Standard price | £239.99 | £269.99 | £30 lower for B300 Pro in this colour comparison |
Sources: B300 Pro UK listing and C300 UK listing.
The B300 Pro page gives both a 5 cm adjustment span and 42–47 cm endpoints. Its published minimum is 1.5 cm shorter than C300’s listed 43.5 cm lower figure. That supplies a useful shortlist criterion, although it does not establish the resulting clearance for your individual thighs.
The standard C300 has a different documentation problem: its page lists a depth range and describes adjustment in its FAQ, while model comparisons have presented different information about the base chair. Confirm the exact UK version rather than treating every C300 listing as interchangeable.
A useful choice around £250
For someone coming from a chair whose seat is too deep, B300 Pro’s published range is a concrete reason to try it. Set the seat so its front edge clears your legs, then assess whether the moving lumbar section contacts your back where you want it.
For someone who changes position frequently and prefers support designed to move with the back, C300 is the more relevant candidate. That is a reason to shortlist it, not proof that every user will like the pressure of its lumbar section.
The lumbar-control comparison explains this distinction across Sihoo models. The HSE workstation checklist provides the broader setup checks for feet, seat, backrest and working reach.
Price and availability deserve equal attention. B300 Pro Black Standard was listed at £229.99 but was unavailable in the checked variant data. Using that figure as the current buyable alternative would exaggerate its price advantage. The White listing supplies the available comparison in this article.
Ordering questions
Is B300 Pro the same chair as C300 Pro?
No. B300 Pro, standard C300, original C300 Pro and C300 Pro V2 have separate UK product pages and control layouts. Use the full model name on the order and invoice.
Is B300 Pro £20 cheaper than C300?
Not with the selected available variants used here. White B300 Pro at £239.99 is £10 below Black C300 at £249.99, or £30 below White C300 at £269.99. The £229.99 Black B300 Pro listing was unavailable when checked.
How short is B300 Pro’s published seat-depth setting?
The UK specification lists 42–47 cm, so the reported minimum is 42 cm. Compare that endpoint with your supported sitting position; the 5 cm span alone would not establish a minimum.
Should the 6D versus 4D label decide the purchase?
Only if the additional pad positions solve a problem at your desk. Check armrest height, position and spacing in the posture you actually use; extra movements can also make setup more involved.
Can a code be added to either advertised price?
Check the current code terms and the retailer’s final total. A listed sale price does not establish eligibility for a second saving. The B300 Pro White offer and standard C300 offer describe the selected purchase routes.
Sources and scope
Sources were checked on 7 October 2026. Specifications and availability are manufacturer-reported. Desworthy calculated the £10 and £30 price gaps from the named available colour listings, excluding delivery or an unconfirmed code. For returns and part coverage, check the main policy and after-sales policy; change-of-mind return transport is not assumed free.
Image credit: Sihoo, product photograph.
Note: This article is for reference only.