These end caps fit 6-bolt E-sync hubs with rare 10x135mm thru-axle spacing (example: DT RWS), and Shimano HG or SRAM XD/XDR cassettes. 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 10x135mm thru-axle hubs and Shimano HG or SRAM XD/XDR freehubs. Not compatible with tradtional 135mm hubs with quick-release skewers. Not compatible with any Centerlock hubs. Not compatible with 142mm, 148mm, 157mm, or single-speed E-sync and Neo hubs. Not compatible with Shimano Micro Spline hubs. Not compatible with M-pulse hubs.Technology:E-sync:- E-sync hubs are built to last, including under the higher torque and weight of eBikes. A 6066 alloy shell, heat-treated steel ratchet ring, reinforced pawls, and full Enduro bearings rovide brute strength, while 8.18° engagement provides the speed.