bugdevheli,
The bearing is a flanged bushing
[see Tuflite Bearings] . The shims are located between the journals and the thrust washers. The addition of shims causes the friction between the non-teetering thrust washers and the flanges on the bearing to be reduced.
The above better be correct, because I'm waiting for a quote right now on these bearings for the Constant Velocity Joint w/ Hub Spring Rotor.
Dave J.