This chair adjustment mechanism pedal office chair part allows your chair to be heightened or lowered. The mechanism allows for a +17 degree angle in the back of your chair and a 2.5 degree angle forward. The part comes with one piece that is black and includes one pedal to adjust height of chair and one component to adjust front and back angle of the chair. The centre hole is standard size for chairs and stools. The width between the screw holes is 151.5mm, the length between the screw holes is 257mm.