... NTN KOYO NACHI BEARINGSWe manufacture quality Deep groove ball bearing , Nonstandard bearings , Special Bearings , Roller skate ... Internal elimination code: C0, C2, C3, C4, C57.Bearing material: bearing steel (9Cr18), stainless steel(AISI440C, AISI304, AISI316), ceramics8. ... Keeper: stainless steel, PTFE, nylon9.Bearing ferrule and ball hardness: 59 - 63HRCExplanation:SKF 6000 ...