-The Wombolt features a unique 2 piece design that uses a single bolt and proprietary wedge to attach the arms together and uses a 22mm tubular chromoly spindle. The arms have been 41Thermal heat-treated for added strength. Compatible with sprockets with a 15/16" center bore. Not compatible with Fly, Profile or Tree sprockets. Lifetime warranty from Odyssey. 22mm bottom bracket sold separately.