High quality chromium plated steel track nuts, integral serrated washers revolve independently of the track nut. 14 - 19 mm spanner required (dependent on nut diameter) Sizes are the axle diameter that the nut screws on to Most Common Applications: - 5/16 - Vintage / traditional kids bike front wheels - 9mm - Modern Shimano type front hubs - 3/8" - Most common size, front rear std MTB, hybrid, kids etc bikes - 10mm - Modern Shimano type rear hubs - 14mm - BMX larger diameter hubs Please check size carefully All wheel nuts supplied in pairs ( 2 nuts as in the picture ).