The Faithfull Varipitch Holesaws are manufactured from bi-metal material with hardened teeth made from high speed steel and a variable tooth pitch for fast smooth cutting. Bi-metal holesaws offer increased safety as they will not shatter under load. They are ideal for use on a wide variety of materials including wood, chipboard, plywood, non laminated plastics, plasterboard and non ferrous metals. Suitable for use in most variable speed power drills.Diameter: 21mm