This is a pair of (2) Patented VRP XV4 Pistons. The pistons come with the Transition Valves (not installed). The Rebound booster hole has been precision drilled to the exact size our testing found to be the best all around setting. This yields excellent results that are proven on a variety of track surfaces. From rough, blown out tracks, to smooth, indoor clay, the VRP Piston makes a positive difference and gives you a Big Advantage over the competition!Simple to understand! The Pistons are designed to increase the Rebound only. They do not change the compression from what you would have running stock 8 hole 1.2 pistons. No crazy set up changes. No scratching your head if they work or even made a difference. Anyone who has run them will tell you it was better from the moment they squeezed the trigger! No questions! .Amazing!You will feel a difference in the piston because it is designed for the oil to flow through the holes instead of around t