Sierra Comfort SC-0131 Balance Ball Chair with Backrest, 20 Ball", Black Lightweight, hard plastic chair base with backrest Four wheel casters for ease of maneuverability 20 inch rubber balance ball, as used for core and strengthening exercises Product Dimensions: 23"(l) x 21"(w) x 31"(h); balance ball height (weight in base): 23"; product weight: 11 lbs.; balance ball diameter: 20" Suggested user height: 5' 2" - 6' 2"; weight capacity: 300 lbs