hybrid bearingBearing rings and rolling material to use with AISI SUS440 stainless steel ( domestic number: 9Cr18) by vacuum quenching and tempering treatment Cage and ring frame material is stainless steel AISI304 ( national numbering: 1Cr18). Stainless steel bearings and plain bearings bearing rings and rolling material to use with AISI SUS440 stainless steel ( domestic number: 9Cr18) by vacuum quenching and tempering treatment, compared to steel, a stronger anti-rust, anti-corrosion select the appropriate lubricant, dust cover, etc.Visit more: www.xzbearings.com/en/hybrid-bearing-131.html