Cone spanners. Thin, open-end spanners designed for adjusting the cones in wheel hubs. These vary in sizes from 13mm up to 22mm. The spanners need to be this thin (about 2mm only) because of the very small gap between a cone and a locknut/spacer and/or very minimal exposure of a cone outside a hub. Typically the front hubs will have cones with 13mm flats, whereas the read cones will feature 15mm flats. Nonetheless the cone flats can be 19mm or even 22mm wide –typically found on BMX bicycle axles. Cone spanners should not be used for tightening any other nuts as they can be easily dented or warped because of the fact that they are relatively thin.
