... .Styles:OPEN,Z,ZZ,RS,2RS,2RZ.. door bearingbearings for windows and doors:1.Material:chrome steel Gcr15 or other optional2.Styles ... ,ZZ,RS,2RS,2RZ3.Tolerance:ABEC-1, ABEC-3, ABEC-5, ABEC-74.Vibration :V4, V3, V2, V15.Radial play:C0 ... ) steel8.Application: doors, windows, wheel chair, skating shoes, textile machine and so on. bearings for windows and doors