The pro 4 rear hub 14812mm boost from hope is the same as the standard pro 4 hub just designed to fit 148mm boost spacing with hopes proven reputation for bullet proof quality you have the security that this will be the heart of a strong and reliable wheel it runs on sealed stainless steel cartridge bearings with a 12mm axle and a 4 pawl ratchet system with 44 tooth engagement for near instant power transfer the hub shell is machined from forged aluminium billet with standard 6 bolt disc mo