... choice, also called ball bearing cage,ball bearing bushing,ball bearing bush,ball retainer & Die parts ... 01~0.002mmMaterial: plastic (resin ),aluminum alloy(bushing),copper(bushing),steel(ball).Hardness: 62~67HRC,spherical degree ... can decrease fatigue damage causing by rolling contact and side damage on machine parts and ... you reviewing the information.More details,pls contact me(Cindy).I'm glad to give ...