Stan's E-Sync Freehub Body E-sync hubs are built to last, including under the higher torque and weight of e Bikes. A 6066 alloy shell, heat-treated steel ratchet ring, reinforced pawls, and full Enduro bearings provide brute strength, while 8. 18deg engagement provides the speed. Features Fits E-sync hubs and includes pawls, springs, pawl retainer, 0. 5mm freehub spacer, 1. 8mm cassette spacer, and freehub seal Bearings are pre-installed Also compatible with Neo and Neo Ultimate hubs as a more durable upgrade | Stan's No Tubes | Stan's E-Sync Freehub Sync Freehub Microspline Black | Aluminum