... and specifications for your choice, also called ball bearing cage,ball bearing bushing,ball bearing bush,ball retainer & Die parts & die fittings ... : 0.01~0.08Shrink fit : 0.01~0.002mmMaterial: plastic (resin ),aluminum alloy(bushing),copper(bushing),steel(ball).Hardness: 62 ... can made of other material ,just like ceramic,plastic etc.)NO 1: Plastic bushing (blue,white colour;NO 2:Aluminum bushing ...