The White Industries Eccentric ENO is the simple clean answer to ones vertical drop out chain tensioning dilemma on a single cog bike. Flip/flop polished hub shell with fixed threads on one side and freewheel on the other. The hub fits into the drops in an offset position and can be rotated up and back thereby tensioning the chain. Once the chain is tensioned, securely fasten the bolts and you have ENO'd your ride. Sweet!