Dernord 12V 600W Immersion Heater Submersible Water Heater Element Stainless Steel Heating Element with 1 Inch NPT Fitting Double U Type 12v DC heater connects with batteries, solar panels, hydroelectric generators and wind turbine dump 1" NPT flange fits USA standard water tank or your own custom heater tank UL and cUL listed to the safety standards Stainless steel surface has electropolish Supplied with silicon sealing washer which is flexible and waterproof