Using your fingers, or a 12mm thru axle, lever the push fit non-drive side end cap off.
Once the end cap is off, slot the 12mm allen key in the non-drive side, and with the 17mm cone spanner turn the cone spanner clockwise to loosen and remove the drive side end cap. NOTE– the drive side end cap is reverse threaded (lock direction printed with arrow on end cap).
Once both end caps have been removed, slide the existing freehub off, and remove the silver spacer which sits between the freehub and drive side hub bearing.
Clean the ratchet ring and outer bearing with a clean microfibre cloth and apply a small amount of light bearing grease.
Slide on the new spacer and freehub onto the axle. Gently spin the freehub with your fingers to get it seated.
With the correct end caps selected*, install the drive side end cap finger tight (reverse thread, so turn anti-clockwise).
With the 12mm allen key inserted on the non-drive side and 17mm cone spanner on the drive side, tighten it up to approximately 8Nm.
Finally, replace the push fit non-drive side end cap.
* If you are replacing the freehub with what was originally supplied, you can re-use the end cap. If swapping from Shimano MicroSpline to SRAM XD or Shimano HG, a new specific end cap is required*. Shimano MicroSpline end caps have "For MicroSpline use" printed on them and come packed with the freehub. Shimano HG and SRAM XD end caps only have the thread direction printed on them.
** When ordering a freehub direct from us, please tell us, by adding a note at the cart page, which freehub you are swapping from and to - e.g."Swapping from MicroSpline to XD". This will ensure we include the correct end cap with your freehub order.