Radium Rotary Engine Injector Seat (Single) - Mazda RX-7 FD/Cosmo JC (13B/20B)These are the same machined aluminum injector seats used in Radium fuel rails for Mazda Eunos Cosmo and RX 7 rotary engines. They are required when converting the OEM 16mm injector seat's counterbore to 14mm which is more common with popular injector lower O rings. They simply "pop" into the OEM injectors bore. They were designed specifically to be compatible with or without the OEM fuel injector diffusers installed. They seal to the machined injector