This rubber bumper seat has an extra piece of fluted rubber at the front and back of to give it a cushioned bumper for added safety. The dimensions of the seat are 24in x 6in x 11/16in or 30 1/4" hanger to hanger. It is made with EPDM rubber, welded triangular hardware and an insert to resist vandalism. EPDM: Ethylene-propylene-diene-monomer is a synthetic rubber material which helps prevent crazing, cracking and oxidizing. Natural rubber is often made from recycled tires etc, and you are never sure what is in the actual rubber.