Some basic differences between the original and current versions of clutch bearings
If you are replacing the clutch release bearing in a Mini that has not been apart since new, you may notice that the replacement bearing looks quite a bit different than the original. The 1960s and '70s bearings had a wide thrust surface, while today's replacements have a much narrower surface that contacts the plate on the clutch diaphragm spring. This newer design has been in production for many years and has proven to be reliable replacement.
GRB238, original version bearing
GRB0238, modern version bearing