Bi-metal Hole Saw. 3-5/8" actual hole size. Cut through steel, tin, aluminum, fiberglass, wood and plastic. Deep 1-5/8" (41.3 mm) cutting depth allows for cutting through 2" x 4" 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 backplate minimizes vibration for smoother, easier, less tiring cutting. Made in USA.