thats a NTN 6203 18,000 rpm bearing same as the rear rotors on supercharger but with rubber seal, mine went 120,000 miles before I change them. being suitable for SLR mclaren and sl65 means, that pulley withstands engines acceleration with more than 600 in torque for years, but anyone with larger crank pulley overdriving all bearings should check bearings periodically expecting shortened bearing life, but mine is stock crank.