A Flip Flop rear track hub (threaded on both sides) Although they were designed to be used on the track,they are used by the majority of couriers in London, because of their durability. You can fix different sprockets on each side. The sprocket is secured by the use of a Shimano lock ring (not supplied). The normal chainline is approx 42.5mm from the centre of the hub.
The Axle is 14mm down to 12mm on the ends. 10mm Flats are machined where the axle fits into the dropouts for secure location. The flats also stop the axle from spinning when the bolts are tightened/removed.
Available in Black and Raw. The Raw is as it says straight off the machine.