CX Nock Collar is a very light weight aluminum ring that slides over the back of your arrow shaft and held in place with your pin insert. 

The collar provides an incredible amount of strength to the back of the arrow and does a great job of protecting the back of the arrow from cracks caused by arrow impacts. 

Pair with a Pin insert and the back of the arrow is almost indestructible* from other arrow strikes. 

*This is not a guarantee, only Chuck Norris is indestructible.