HARD Motorsport - BMW E46 M3 355mm Big Brake Cooling Backing Plates (E46BKPLATE-355)SOLD IN PAIRS Big Brakes require Big Cooling!!! When upgrading your E46 M3 brakes to a BBK, you should get cooling plates that were specifically designed for the big 355mm oversized rotors to provide efficient cooling and fitment. Our all aluminum E46 M3 BBK Brake Cooling Backing Plates for the 355mm rotors features our large 'pocket' to allow for more air flow directly into the rotor hat, where you need it. Forcing cool air through your rotors is the