Bearing, R3-ZZ 

Bearing for ball bearing steady rest and follower rest.

Size is 3/16" (ID) x 1/2" (OD) x 5/32" (width).

ID: 4.762 mm = 0.1875 in (3/16)

OD: 12.7 mm = 0.5 in (1/2)

Width: 3.967 mm = 0.1562 in (5/32)