Size: 626Z (Inner Dia.=6mm, Outer Dia.=19mm, Thickness=6mm)Shield on SINGLE SIDE of the bearing for easy lubrication and maintenance while protecting from dirt. for vertical installationChromium Steel long-life bearings, smooth and low noiseABEC Tolerance 1 (P0), Z2 Noise Level for most general usePre-Lubricated, Easy to maintain.