The MRC SR8-ZZ (or R8-ZZ) is an extra-small, inch-series deep groove ball bearing. Featuring double metal shielding to keep dust out and retain grease, this stainless-steel bearing is typically used in miniature applications, medical instruments, and light industrial equipment. Dimensional Specifications Inner Diameter (ID): 0.5000 in (1/2") Outer Diameter (OD): 1.1250 in (1-1/8") Width: 0.3125 in (5/16")