Item No.: MIB3T~MIB16T, SIB3T~SIB16T, AIB3T~AIB16TBALL: 52100 Bearing Steel,Heat Treated,Hard Chrome Plated,Precision GroundRACE:MIB: Low Carbon Steel, I.D.Protective Coated for Corrosion Resistance,Oil coated Mfr.Option-Stailess Steel, Heat Treated.AIB: Alloy Steel,Heat Treated, I.D.Protective Coated for Corrosion Resistance,Oil coated Mfr.Option-Stailess Steel, Heat Treated.SIB: Stainless Steel,Heat Treated and Oil CoatedPhone: +86-592-580 8851 / +86-592-580 7618Email: sales@ldk-bearing.com ; benjamin@ldk-bearings.com