... standard:ASTM A269,A249,EN,TP304,321,316L.... Appliance:electric heater,heater elements O.D.:from 6mm to 23mm Features: 1) Production ... by company bring no worry to the customers in terms of the quality of the welding seam, the interior and exterior surface ... of the pipe/tube as well as the property of extensibility. welded stainless steel pipes for electric heater