Well, didn't know it when I purchased it, but the 20mm front kit is for taking 100mm hub to 20x110mm spacing. The problem was that I had a boost hub, but an endcap was lost in shipping. Luckily the bicycle shop owner used his lathe to take the NDS cap down 5mm and added the same shoulder.
Hopefully they will get the boost kit up soon.

needed to convert a front wheel from 100 X 15 to 100 X 12, as the front wheel has and SRC hub these caps allowed me to change it to 100 X 12, just, by hand, pulled the old caps off and put these on, that's it, very simple conversion

I was looking for a 27.5+ wheelset for a Cannondale Trail Two that has a 141 QR frame. I was able to get a SRC rear hub that was 148 TA and the QR Rear Hub End Caps worked perfectly. Very pleased with the customer service and quality of the products! Thank you!