The axles and freehubs are interchangeable between all the Spin Doctor rear hub models,(Note: Although they are not cross compatible with the original Spin Doctor parts). This interchangeability allows customisation of the Spin Doctor hubs to suit your needsSpin Doctor Solid Axle:Several riders have asked for a nutted axle version of the popular Spin Doctor Disc Cassette hub... so here is the optional conversion kit.KIT;185mm x M10 Cr-Mo axle.Steel bearing covers and locknuts.Alloy M10 nuts.Rear - M10x135x185mm with bearing covers and axle nuts.Weight: 140gSolid Cr-Mo axle KIT option with CNC machined bearing covers and M10 nuts included.This kit allows the Spin Doctor to be run with BMX style chain adjusters.Note: M10 axle kit also fits optional 14mm Axe Men convertors to allow Spin Doctor to run with 14mmx135mm frames..