I bought a 1500 watt at Lowes. it was 9" long. it screws into the heater tank. be sure to unhook the RV from electricity then open a hot water faucet then remove the drain plug to drain the tank then it's just a matter of unhooking two wires and unscrewing the old element. making sure the gasket came off with the old one. install the gasket and screw in the new one and hook the wires back up, install the drain plug and fill it with water. check for leaks, hook up the electricity, turn it on and enjoy hot water.