Calico Designs Deluxe Task Chair in Black with Gray base 18509 Overall Dimemsions:21"W x 21"D x 30.5" - 35"H Pneumatic Seat Height Adjustment: Min.16", Max 20.5" Seat Dimensions:16.5W x 15"D Backrest Dimensions:16"W x 10"H 21" Diameter 5 Star Nylon Base, Casters for Mobility Overall Dimemsions:21"W x 21"D x 30.5" - 35"H Pneumatic Seat Height Adjustment: Min.16", Max 20.5" Seat Dimensions:16.5W x 15"D Backrest Dimensions:16"W x 10"H 21" Diameter 5 Star Nylon Base, Casters for Mobility