These are the same seat shells we sell for cars, mounted on a gas lift office base. That means the sizing works exactly as it does on a car seat: measure across your hips sitting down, and go by the waist band where the product lists one.
Measure yourself sitting
1Sit on a hard, flat chairFeet flat, back straight against the chair back.
2Measure across your hipsThe widest point, side to side, sitting down.
3Think about how long you sitEight hours at a desk is a different job to a two hour stint in a car. Err wider here.
Size up rather than down for a deskIn a car, a snug seat is doing its job, holding you in place through corners. At a desk there are no corners, and a shell that grips your hips is simply uncomfortable by the afternoon. If you are between two sizes here, take the wider one.
Reclining or fixed back
For a desk chair you want reclining, and nearly all of these are. A fixed back shell makes sense on a sim rig where the whole point is being held still, and makes very little sense in front of a keyboard.
Armrests
This is the decision people regret either way, so think about it properly. Without armrests looks better and is the right answer if you pull right up to the desk or you are using a wheel and pedals. With armrests is noticeably more comfortable across a full working day of typing.
The base
The base is the only part of these chairs that is not a car part. Ours come in black or chrome, in an even split, and the choice is purely how it looks in the room. All of them are gas lift, so seat height adjusts the same way any office chair does.
Because the height adjusts at the base, the shell height matters less here than in a car. What matters is the width across the hips and the depth of the bolsters.
Head support
Most of these have no head support, which is normal for a desk chair and means you can see over your shoulder without moving the whole chair. A handful have it, and those suit a sim rig or anyone who leans back to think.
Trim, for a room rather than a car
The trim choice is different indoors. Fabric, cloth and spacer fabric breathe, which matters when you are sat in the same chair all day, and they do not get cold in the morning the way vinyl does. Houndstooth, tartan, corduroy and basketweave are here because they look right in a room and they are what most people pick.
Alcantara and suede feel the best and mark the most. Leather and vinyl wipe clean, which is the argument for them if the chair is near a workbench rather than a desk.
These are not car seatsOnly a handful of these carry any approval, and where they do it is Gaming and Sim Racing or Road and Track. An office base is not a car mounting. If you want the same shell in a car, buy it from the seat range with the right fixing type, and we will match it.
Matching a chair to a car seat?Tell us which seat you have and we will find the same shell on an office base, or the closest thing to it. Send your seated hip measurement if you want us to check the size. Call 0115 989 3488 or email Sales@GSMPerformance.co.uk.
All figures read from our own product data for the office and gaming chair category, checked 2 August 2026. Counts change as stock moves.
