The Mini's rear subframe is rubber mounted. These standard rubber bushes fit the front of the rear subframe on MKIV (1976) and later Minis. These models also use 4 of the 2A5818 for the rear trunion of the rear subframe. Polyurethane (stiffer, much longer lasting) bushes are now available for the rear subframe trunions- see 21A2560/poly.
Cars manufactured before 1976 used the same bush (2A5818) at the front and rear of the rear subframe, 8 per car.
Starting in 1976 (MKIV) the front trunion bush was enlarged, that bush (21A2560/POLY) is now available in Poly. These later cars use 4 of each 2A5818/POLY and 21A2560/POLY.