The magic to Industry Nine's amazing engagement comes from its mastery of materials, design, and machining of its Hydra Freehub Body. So whether you're are changing component groups and need to convert your existing Hydra mountain freehub body or you just want to keep a spare one on hand so you never miss a ride, now you can. This complete kit includes everything you need to swap the freehub (shell, spacer, bearings, pawls, springs, and seal). Available in Shimano 9-11 speed HG or SRAM 11-12 speed XD.