Thetford 94163 RV Sewer Hose 4″ Plastic Bumper Plug w/ BarbsThis bumper plug is designed to seal off the end of a 4-inch square bumper on an RV. The bumper typically serves as storage compartment for sewer hoses, fishing rods, or other elongated items. The plug is designed to prevent the contents from falling out during transit, as well as to keep out debris. Made out of durable UV stable black plastic for a secure fit.Friction-Fit: A series of barbs grip the inner walls of the bumper for a secure fit.Plastic: Made from fade-resistant black plastic.Compatibility: Fits 4″ hollow square bumpers.