... coefficient : 0.01~0.08Shrink fit : 0.01~0.002mmMaterial: plastic (resin ),aluminum alloy(bushing),copper(bushing),steel(ball).Hardness: 62 ... material ,just like ceramic,plastic etc.)NO 1: Plastic bushing (blue,white colour;NO 2:Aluminum bushing(white,cupreous colour);NO 3:Copper bushing(copper ...