water boiler electric heating tube stainless steel heating elements copper heating elements electric duct heater is a kind of heating elements.we put a heating wire in a metal tube amd then the gaps are padding with MGO, simple structure, long-time usage high efficient heater exchange it could easy to bent into many kinds of shape good insulation could withstand high voltage widely used in showers water machine, water dispenser ,water boiler machine,diswashers and various types of heating appliances. insulation: MGO tube material: seamless stainless steel tube welded stainless steel tube copper tube brass tube carbon steel tube usually tube diameter: dia22 dia20 dia18 dia16 dia14 dia12 dia10 dia8 dia6.5 length:10mm to 5000mm surface:nickeled ,passivation ,black, spray Specially dimension also could be made as customer's demands.Pls supply detailed information about what you need. we are warranty the quality for one year at least.