Many of us from time to time need to make repairs or modifications to the Pex plumbing in our RV's.
If you haven't looked yet, while you'll find the Pex crimp rings are pretty cheap, the tool or crimper for squeezing the rings, usually are obscenely priced. Some Rex crimp tools available at Lowes, Menards, etc cost nearly a hundred bucks or more.
When I was going to add a "T" to my main water line just downstream from the water pump for an accumulator tank, I was having trouble locating a sensibly priced Pex ring crimping tool.
After doing some looking, I hit pay dirt. I found this little critter and now have it in my toolbox.
Pex Pocket Crimper
It's simple to use. Just put it position on the tube with the crimp ring, and squeeze the end with a vice grips or big channel locks.
You can also get a go/no-go gauge that will tell you if your ring is crimped enough or not.