These Filmtools Stairclimbers (Pair) for Filmtools Senior Carts are made of fully extruded aluminum outfitted with teflon skid pads. These stairclimbers will attach to any Filmtools Senior Convertible Carts. The reason you would want to buy this is because our product will not crack. Competitive models will crack because they are made of cast aluminum or pot metal. To add further value, we will include mounting hardware for you.