Set includes a 5-inch rubber roller attachment that has two 8mm steel shanks to fit your drill. Includes 16mm, 20mm, 30mm, 35mm, and 45mm attachable rubber suction cups. The suction cups make fitting and seating various valve sizes easy. Use with your existing electric drill and automotive valve grinding compound (not included) to correct surface irregularities and to remove sub-surface damage on your new valves when working on a top-bottom rebuild.