KOKEN IMPACTO nut mounting bits are made of high quality metal, resistant to wear and tear. The set comes with three bits - 17, 19 and 21 mm. Each nozzle is painted in a different color. The weight is 23.2 ounces. All attachments have a universal round mount where you can attach them to a screwdriver or any similar impact type tool. These bits are designed primarily for tightening or loosening nuts on car wheels, so they are extra durable. The surface of the nozzles is rubberized - this is done in order not to damage the wheel disk during its installation. Each nozzle is clearly marked with the thread size.