The Faithfull 9 Piece Electricians Professional Holesaw Set contains the six most frequently used electricians holesaw sizes, along with two arbors and an adaptor. These high speed steel bi-metal saws have specially hardened variable pitch teeth for fast smooth cutting. Bi-metal saws offer increased safety as they will not shatter under load. These holesaws are used to cut perfect holes in 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. Supplied in a sturdy zip-up case. Contains: 6 x Varipitch Holesaws: 16, 20, 25, 32, 40 and 51mm.1 x 3/8in Hexagon Arbor for Holesaws 14-30mm.1 x 7/16in Hexagon Arbor for Holesaws 32-152mm.1 x Sturdy Adaptor.Additional Information:• Material: Bi-Metal• Pitch: Variable