The same tried and tested quality as the front hub. Pure fixed wheel luxury. 100% made in USA. Phil Wood introduced the now-standard Field Serviceable Axle (FSA) in 1991. The FSA design enables the axle to be separated from the hub after unthreading the end caps. The axles are threaded externally, with the end caps threaded to exactly match the axle thread. For optimal performance, it is recommended to use the Phil Wood track cog. Specification for the threading is 1.370x24 tpi, but Phil Wood hubs will accommodate most high quality cogs. Some cog manufacturers are making cogs that are not ideal for use with Phil Wood hubs due to their thickness. For this reason, we do not recommend using Surly or Euro-Asia cogs with Phil track hubs. Lockring threads are Italian (Campy compatible). Specifications: 100% made in the USA High Flange (HF) 120mm spacing (spacing conversion kit available) 32h | 36h Warranty note: Phil Wood track hubs are designed to be used with Phil Wood high quality cnc track sprockets. Using any other brand of sprocet than Phil Wood's own will invalidate your warranty.