2-1/4", 57MM, Bi Metal Hole Saw, Optimized Tooth Design For Superior Performance While Cutting Metal M3 Steel Provides Faster Cuts & Longer Life, Thick, Hardened Backing Plates Prevent Warping At Holes & Increases Cycle Versatility Of Deep Cut Style Allows Users To Cut Either Wood Or Metal, Applications Include Plumbing, Electrical, HVAC.