Camcos 4500W 240V screw-in type low watt density water heater elements are better suited for areas with problem water (hard water, lime, etc.) Most LWD elements are a fold-back style and provide no loss of efficiency yet reduce lime deposit buildup. This screw-in element has 1-3/8" thread and is made for State Industries manufactured Duron Tank Water Heaters. Also used in Sears Duron tank water heaters. Each element includes two gaskets. The replacement element must be the same voltage and wattage as the element being replaced. Never exceed the nameplate rating on the water heater.