This sale is a NOS GM AC DELCO 18004889 rear wheel cylinder for a lot of GM cars from 1964-78. The original part number for this cylinder was 5469321 which was replaced by 5462939 and then changed to this part number 18004889. This is correct replacement for 5469321 which is the correct cylinder for 1964-66 GM A-Body cars. This will work for all 1964-72 A and F body cars which is GTO,442,GSX,Chevelle,Camaro,Firebird,Trans Am,etc,etc. The only difference is the 15/16 diameter piston/seal/bore which is better anyway. Lol. I know because I have used these on 68/72 GTO and Trans Am.   I only have Pontiac parts books so please check your application for other GM car lines before buying. Buyer to pay 9.00 shipping and payment in 2 days by PayPal or cash in person.  Thank you.