These end caps fit 6-bolt E-sync hubs with 142mm, 148mm, or 157mm axle spacing and SRAM XD/XDR or Shimano HG freehubs. The non-drive side end cap includes a low-friction U-cup seal that snaps into place and stays secure even when your wheel is removed from your bike. Compatible with E-sync, Neo, and Neo Ultimate 6-bolt hubs with 142mm, 148mm, or 157mm and Shimano HG or SRAM XD/XDR freehubs. Not compatible with Shimano Micro Spline freehubs. Not compatible with any Centerlock hubs. Not compatible with 135mm or 150mm E-sync and Neo hubs. Not compatible with M-pulse hubs.