Any original side fitting radiator with the sender unit in the bottom on SPI 1275cc models from 1991 on. This 15lb radiator cap has a top rubber seal on it to ensure an air tight fit creating a vacuum as these models were fitted with an overflow bottle/expansion tank. This cap has a small vent which will open and draw the fluid back from the overflown bottle into radiator from the overflow tank as it cools down.
Because the overflow tanks are no longer available some customers have reverted back to earlier 15lb caps to dump water straight to the ground but we have also found these caps can be used on cars without overflow tanks.