Product Detail Features a square contoured hardboard seat with 16 rivets 0.88'' O.D. 18-gauge steel tubing Foot rings 0.63'' O.D. are welded to each leg by 4 contact points at each leg for added 18''H 24''H or 30''H sizes fixed and adjustable with an optional Optional backrest; 6''H x 12''W adjusts up/down and forward/back . The "Lab Stool - 18 Stool with Hardboard Seat - National Public Seating - 6318" is best product for you. We recommended Lab Stool - 18 Stool with Hardboard Seat - National Public Seating - 6318