The 9100 round seat has a full 14” round top and is made up of a special combination of foam for stability and comfort. 9100 & 9120 [20" min / 27" max height] The 9120 has an oversized tractor seat top. Both 9000 Series Thrones feature DW’s newly designed double locking clamp, vise lock seat clamp and an oversized 1” base for added stability.