Tec Line: Cleanroom and ESD have a height-adjustable back that provides 3" adjustment range for both back and lumbar. There's a polished 20" diameter with simple rotation/lock for height variation of the foot ring for the stool. Cleanroom offers a black nylon five-star base. The base for both Cleanroom and ESD is a polished aluminum five-star base. Casters with soft wheel braking casters for hard floors are standard specifications.