The piston ring is easy to stretch with the piston installation tool. First the installation tool is two pieces take the the cylinder half of the tool with smaller hole facing the base of the rod and piston head. Second put the cone from the tool on to rod of the piston. Third take your new piston ring and gently put even pressure on the ring sliding it down the cone. Fourth once the ring is stretched over the cone you can remove the cone and then gently slide the cylinder up to press the ring back to it's original shape and size (may have the back off the ring a couple times to get it lined up with the groove it sits in). Then you should be done and that piston should be good to go.