This nut is part of several rear axle assemblies that have a 9mm axle. It is located on the drive side of the axle. In the past this nut was only available as part of a rear axle assembly (V2250201, V2250301, V2250501, +). It is used in several Mavic rear hubs including but not limited to: Ksyrium Pro, Ksyrium SLS, Ksyrium Elite S, and Cosmic.