The Starrett Fast Cut Bi-Metal Holesaws combine a new tooth material and a 5.5 TPI/25mm tooth form, with increased resistance to heat and wear. Providing a smoother, faster cut on a wide range of materials, when compared to the previous constant pitch saw. Specifically suited to cutting stainless and mild steel sheet, they will also cut through tubes with a wall thickness of up to 3mm (1/8in). Cutting Depth: 41mm.Starrett FCH0318 Fast Cut Bi Metal Holesaw has the following specification: Diameter: 79mm (3.1/8in).