Used to remove 1/2" 3/4" or 1" compression rings from fittings so you can reuse the fitting.
Cut the tubing off as close as possible to the fitting. Insert the round nose of the tool into the fitting with the cutting blade outside against the ring. Squeeze until the ring cuts. Rotate 90ish degrees, cut again, then rotate in between and cut again. Ring should now slide off. To get the pipe free often you need to make multiple cuts into the plastic - do NOT nick the fittings or they may leak. By cutting the plastic multiple times at multiple locations the plastic pipe will expand enough to slide off easily.