These grinding wheels are designed to be used with the Dremel SC402 Mandrel. The Dremel Easy Speedclic (SC) mechanism makes wheel changing easy, simply pull, twist and release. This feature makes accessory changes such as this 6x faster than using a standard mandrel It makes accessory changes 6X faster than using a standard. The indent on the disc allows the mandrel to retain distance from the workpiece when in use face down. This allows for grinding on a flat surface. These wheels are ideal for use on metals, stainless steel, aluminium, brass, ceramic, copper hardwood, plastic, softwood and stone. Features and Benefits Shank diameter: 3.2 mm Working diameter: 38 mm Grit: 320 Width: 35 mm Length: 35 mm Height: 4 mm Material Applications Steel Stainless steel Hardened steel Brass Gold Aluminium Silver Cast iron Copper