Most kits are a series of different sized plastic sleeves about an inch long to fit various sizes of tubes. They're split so you can get them around the tube. Once around the tube you push them into the fitting to expand a circular coiled spring. They're sort of tricky to use because you have to both push in on the sleeve and pull the two tubing sections apart. There are also "all in one" types of tools but they're even harder to use especially if you don't have alot of room. The sleeve type should be $20-30. The tool is not needed to reconnect the tube sections. Just replace the two o-rings and push them together. There should be a little snap as the spring goes over the tubing flange.