Syntace MicroAdjust end caps ensure your Syntace HiTorque hubs are equipped with the latest updates. First GEneration Syntace hubs were not equipped with MicroAdjust end caps, but luckily they can easily be retrofitted should your's not alredy have this update. The MicroAdjust end caps allow quick adjustment of the axial bearing pressure without fiddly micro shims. 

If you want to convert your hub to MicroAdjust, all you need is the MicroAjust end cap. If you are also changing axle standard in the process, you will also require the respective second end cap as a non MicroAdjust end cap.

Installation process can be viewed here: 
http://www.syntace.com/misc/popup/detail_videos.cfm?pk=1449