Part Number: RK643. 2x EBC RK643 Rear Brake Rotors. The EBC RK643 is a rear brake rotor engineered specifically for the first-generation Mazda Miata (NA) produced from 1990 to 1994. 1990–1994 Mazda Miata (NA, Base/LE/SE/M‑Edition, 1.6L I4, RWD, Rear).