We recommend you use 3-6 discs per mandrel for best performance. These discs will produce a uniform finish that is easily controllable. With great conformability and flexibility, these discs will enable you to easily finish detailed or hard to reach areas. They run clean; no chemicals or compounds required. Also, runs cool and so is safe for delicate pieces. These discs are sold per dozen and measure 3/4" in diameter. The recommended speed is 15,000RPM to a maximum of 30,000RPM.