... retainer,which is excellent performance of hardness,glossiness,resistance,service-life. This product is made of copper or aluminum or ... (resin ),aluminum alloy(bushing),copper(bushing),steel(ball).Hardness: 62~67HRC,spherical degree is 0.25UM.Features1. low ... 6.sound quality steel ball retainer with excellent performance of hardness,glossiness,buildiness,abrasion resistance,long service-life. The ...