Pneumatic Seat Height Adjustment: Min.16 in. to Max. 20.5 in. . Seat Dimensions: 16.5 in. W x 15 in. D. Backrest Dimensions: 16 in. W x 10 in. H. 21 in. Diameter 5 Star Nylon Base. Casters for Mobility. Overall Dimemsions: 21 in. W x 21 in. D x 30.5 in. - 35 in. H