Replacement Freehubs for your rear Scrub Hub.
 
Available options:
Sram XD
Shimano HG
Shimano Micro Spline.
 
Note: XD and HG share the same axle. To convert between these types, only the Freehub is required.
 
Shimano MicroSpine has a unique axle. Therefore switching between MicroSpline and HG / XD (and vice versa) requires a conversion kit.