... hardness,glossiness,buildiness,abrasion resistance,long service-life. The bushing has 3 types,which is made of steel( it ... ,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 each type ... 'm glad to give you the best service. Aluminum/Brass/POM bearing cage