The ball bearings originally fitted to the rear of standard Minis have now been replaced with the same taper roller bearings as used on the Mini Cooper S. Additionally, the separate spacer has now been designed into the bearing inner race, so a separate one is no longer used. This part number is always genuine Timken, with seal and cotter key included. Other suppliers' kit that say "taper roller" may not be by Timken, the original manufacturer, so inquire when comparing prices. Use one kit per side.
See also the later GHK1805 Timken kit.