White Industries ENO Eccentric Hub

White Industries' Eric's Eccentric ENO hub is used to convert a multi-speed bike with vertical dropouts into a single-speed/fixed gear.

Most bicycle frames today are made with vertical dropouts, so converting a bike into a single speed presents the problem of how to tension the chain. The eccentric rear hub allows the rider to adjust the chain tension by rotating the elliptical axle ends up and back in the dropouts. As the hub rotates back, the chain is pulled into tension.