From the manufacturer:
This is the original diaphram as fitted to the Mk2 Mini, and comes with the necessary springs to attach it to the seat frame.
The Mk2 Mini was introduced in the Autumn of 1967, and among many other body and mechanical chnges the design of the seats was altered. The seat frames were retained from the earlier Mk1 models, but the seat covers and internal foams were redesigned to give more comfort as well as giving the seat a different appearance to earlier models.
Special order, allow 3-4 week delivery time.