Um, buddy, you need to go back to the hardware store and get a 26mm external snap ring. The one you have is an internal ring. It is meant to be put inside of something. It will probably not work for long how you have it. There is too little contact area to keep it in place.

The better (and easiest) thing to do is to call St. Charles Isuzu and order a few. They are cheap.

Good Luck,
Michael