171⁄2"-201⁄2" seat height. Ergonomically contoured polypropylene shell, a pneumatic cylinder. Chair moves with you to help activate your best sitting position. With an ergonomic seat secured by four air coils that flex and compress as you move, the chair provides controlled movement in all directions from front-to-back, side-to-side and in-between. Chair swivels 360°. Pedestal base has a five-prong construction. Five 2" diameter, dual-wheel, hooded swivel casters.