Bi-Metal hole saws. Cut through steel, tin, aluminium, fiberglass, wood and plastic. Deep 1-5/8 inch cutting depth allows for cutting through 2 x 4 inch wood studs. Extra-tough bi-metal blade - we use the highest grade of tool steel to outlast competitor's blades. That beats premature saw replacement and saves you money. Steam oxide finish - no paint to gum up and slow cutting. The saw runs cooler for longer life and better performance. Extra-thick back plate minimizes vibration for smoother, easier, less tiring cutting.