Bi-Metal Hole Saw, Actual Hole Size 4-1/2" (114.3 mm). 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 oftool steel to outlast competitor's blades.