... can made of other material ,just like ceramic,plastic etc.)NO 1: Plastic bushing (blue,white colour,POMS,POMBS,POMM,POMBM,POMT ... ,POMBT type;NO 2:Aluminum bushing(white,cupreous colour,ALBS,ALS,ALBM,ALM ... ,ALBT,ALT type );NO 3:Copper bushing(copper-colored, CUS,CUM,CUT type).Also ...