Very helpful tool for mounting the piston into the cylinder. Who doesn't know the problem of the piston rings being under so much tension that mounting them into the cylinder becomes a game of patience. With this tool the piston rings are clamped together in the piston. Then the piston is pushed through the tool from above into the cylinder until the piston is completely inside the cylinder. Now the piston is pushed out of the cylinder from below until the piston pin can be mounted. Done. Suitable for pistons from 40mm to 85mm diameter.