This end cap is for 100mm M-Pulse front hubs to be used with forks that use a 15mm diameter axle and 100mm axle width. Only one end cap is required for conversion since your current preload ring is compatible with both 12mm and 15mm axles. Compatible with 6-Bolt and Centerlock. Not compatible with E-sync, Neo, Neo Ultimate, and 3.30 hubs.