The Surly Ultra New Rear Hub offers classic fix/free versatility in a wide 135mm spacing, ideal for touring, singlespeed mountain bikes, or commuters wanting extra tire clearance and wheel strength. With a fixed cog thread on one side and freewheel threading on the other, it gives you flexibility in how you ride. The durable aluminum shell and sealed cartridge bearings provide smooth, low-maintenance performance, while the bolt-on axle ensures a secure fit.