... :OPEN,Z,ZZ,RS,2RS,2RZ.. door bearingbearings for windows and doors:1.Material:chrome steel Gcr15 or other optional2.Styles ... , ABEC-74.Vibration :V4, V3, V2, V15.Radial play:C0, C2, C3, C4, C56.Hardness:59 - 63HRC7.Retainer:PTFE, nylon, PEEK or ... ) steel8.Application: doors, windows, wheel chair, skating shoes, textile machine and so on. bearings for windows ...