All cutting and stripping surfaces are precision machined to produce clean, exacting results High carbon heat treated steel for long life Black oxide finish resists rust and corrosion All models feature holes for looping and serrated tips for pulling wire Strippers/cutters are spring loaded for easy one hand operation and have safety lock (except 730724) Multifunction tools cut, strip and crimp insulated and non-insulated terminals For use on copper and aluminum wire only