... .Material:chrome steel Gcr15,PTFE, nylon, PEEK or (stainless) steel 2.Styles:OPEN,Z,ZZ,RS,2RS,2RZ.. door bearingbearings for windows ... and doors:1.Material:chrome steel Gcr15 or other optional2.Styles:OPEN,Z,ZZ,RS,2RS,2RZ3.Tolerance:ABEC-1, ABEC ...