No need of current-limiting resistor reduces heat resource. No black spot on welding point,free of polish. A built-in voltage regulator ensures constant output voltage,The welding consistency is good. Full digital control with high precision Components and parts from world famous factories ensure quality. The welder is easy to opration and free of complicate educational procedure.The welding effect ia perfect. Primary welding materia:stianless steel,brass,copper alloy,and duralumin. Suitable for electric appliance,watch chain,jewelry,stainless tableware,and hardware manufacturers