These tips are made from alloy and not electroplated, easy to tin and diamagnetic, suitable for lower temperature soldering. Shape::There are total 5 shapes of soldering tips in this set and you can choose the proper one for different soldering needs.Completable::900M Series Soldering Tip for Hakko Soldering Station Tool 936 937 907 Irons Tips, Set of 5 Shapes, Instructions::Don’t leave your iron running for hours and hours if you are not using it. This can make the tip get black oxide cover. Try to tin the tip as it heats. If you leave it on too long or run it too hot it will burn off the solder and go black again. These soldering tips are suitable for soldering stations.