This is a large 57mm caliper piston for a Jaguar E-Type 1971 to 1974, XJ 1969 to 1973. One piston is needed per caliper. The pistons are Plasma Nitrided which will give you the life of Stainless at half the price. The Nitriding becomes a part of the metal and will not flake off or seperate, you can't buy a harder caliper piston. Cross Reference ## 64325438, 19-1162