Back Rake Mechanism – Allows seat height adjustment and the back rest to be adjusted for rake angle by means of a lever. The desired angle is located and then locked off. The backrest height is adjusted by means of a hand wheel.
Permanent Contact Mechanism (PCB) – The seat will go up and down, the back rest will go up and down and in and out, and you can fix the angle of the back rest or leave it free floating i.e. in ‘permanent contact’ with your back
Independent Seat & Back Mechanism (ISB) – You can fix the angle of the back rest or leave it free floating i.e. in ‘permanent contact’ with your back, Independent seat adjustment lockable in various positions. Also features body weight tension adjustment.
Synchronised Mechanism (Synchro) – By far the most common type of action where the back will move backwards and forwards in conjunction with the seat. Fix or free float the angle of the seat and back rest together usually in a ratio of 1:2. So every 1 degree the seat tilts the back tilts 2.
Intelligent Action Mechanism – a relatively new type of chair action where the seat and back will move independently of each other but without the need to set a weight tension.
Body Weight Synchro Mechanism (BWS) – Another new type of chair action which operates in the same way as the normal synchro, but will automatically choose the right weight tension (this can be fine tuned in most cases though).
Seat Slide – Does what it says and moves the seat backwards and forwards, usually by around 50mm
Spindle – This is simply the ‘gas’ (spring) operated column that allows the seat to be moved up and down.
3D Arms – A slightly confusing term as all it means is that the arms will not only go up and down, but will also slide backwards and forwards as well as be adjustable in width.
4D Arms – These will do the same as above but will also have arm pads that will swivel either part or all the way around.
Inflatable/Adjustable Lumbar – Normally this is by inflating an airbag hidden in the back pad of the chair or by having a tension bar that will be adjustable in height.