... for your choice, also called ball bearing cage,ball bearing bushing,ball bearing bush,ball retainer & Die parts & die fittings ... fit : 0.01~0.002mmMaterial: plastic (resin ),aluminum alloy(bushing),copper(bushing),steel(ball).Hardness: 62~67HRC,spherical degree is 0.25UM ... of hardness,glossiness,buildiness,abrasion resistance,long service-life. The bushing has 3 types,which is made of steel( it can ...