Made of all weather and abrasion resistant rubber. The half-oval shape allows for effective fendering action over a wide radius. A metal plate is located inside 4" and 6" projection bumpers for support while the 2" unit comes with one washer per hole. 120" models do not include holes or support material. 120" long bumpers run longer in order to be cut to final length. Custom lengths available up to 10 feet. Installation hardware sold separately.