NOTICE: This is not the 5x10x4 bearing normally used in clutches. The 5x10x3 Ceramic Metal bearing (MR105ZZC/B3) are a high quality steel/chrome bearing with metal shields. Instead of the steel balls they use silicone nitride ceramic balls (Si3N4). These bearings have been tested and proven by many racers. Check your manual for the correct size for your vehicle if you are not certain.