Made of good quality metal material with high speed steel cutting edge for sharp cutting and long lasting. This 25 mm Hole Saw provides good strength and great wear resistance. Used to drill large diameter holes, usually through thin metal boards. This Hole Saw Set can be used for many kinds of metal. Cutting safely and efficiently. The grub screw holds the saw firmly against the shaft of the drill bit so that it revolves at the same speed. Come with a Hex Wrenches for you easily firmly wrench the grub screw.