The seat frame for these late Mk.2 models had a different internal squab spring arrangement. Earlier seats had only a foam cushion, but these seats had a wire support frame attached to the frame itself and then rubber straps which pulled these wires together to create the bucket style shape of the seat. As can be seen here, the rubber straps have hooks which attach to the wire frame arrangement.These wire springs are no longer available, so should they be broken you may need to replace them with our strap and foam kit - part no. SF4025.