This style of rubber diaphragm was originally used on all models until about 1973 when it was superseded by a wire and cord replacement diaphragm. However, this diaphragm can be used on all standard Mini seats built up until 1993 (before the introduction of the seats with twin post headrests) as many find that these rubber diaphragms offer more support and longevity than the wire diaphragms. 

These are easy items to replace individually as part of a seat re-trim. We do not recommend the fitting of new foams and diaphragms underneath old and worn covers, as the renewed tension can damage the covers. Some owners do manage this successfully where the original diaphragms have split, providing the old foams and covers are very carefully removed and refitted.