Medium Universal Chair Seats are made of a special high quality plastic that is crack and split resistant. It is made to stand up to the wear and tear of the toughest classrooms. Dimensions 15" Diameter x 14-1/4" Width. Seats are supplied without holes which allows you to custom fit to most frames that have a flat frame area where the seat attaches. Simply drill your fastening holes through the existing holes in the frame into the plastic. Sand color is stock. Other colors availabe with minimum purchase.