IVY Classic 27066 4-1/8-Inch Bi-Metal Variable Pitch Hole Saw, One Piece Arbor Attached, 1/Card Cuts stainless and mild steel, non-ferrous metal, plastic and wood, 1-1/2-inch cutting depth Bi-Metal construction with M-3 cutting edge, Cobalt Advantedge (Registered Trademark) Variable pitch, positive rake tooth design 4-6 TPI minimizes tooth wear Solid alloy-steel back reduces vibration and convenient, one-piece hole saws save arbor changes. Use with 1/4 x 4-5/16-inch pilot bit: IVY Classic 28114, 28115 or 28136