A wheel PCD is made up of the number of studs that hold your wheel on, and the diamater in mm of an imaginary circle that goes through them all
So 4 x 100 would be 4 studs with a circle diameter of 100mm.
If you're not sure of the PCD of your car, just ask us and we'll be happy to help
I bought this for my FD3S after the original one gave up, it was the most competitively priced radiator for a RX7. Had to move things slightly but fitted with no problems and was able to use the standard twin fans. Only thing for RX7 it doesnt have the Air Seperation Tank take off but I bought something to bypass it anyway.