Dr. Pulley Roller Weights 19mm X 15mmCOMPATIBILITY: Aprilia – Scarabeo 50 4TItaljet – Jet Set 50 4T (Piaggio), Torpedo 50 4T (Piaggio)Piaggio – Fly 50 4T, Liberty 50 4T, Zip 50 4TVespa – ET4 50 4T, LX 50 4T, Primavera 50 4T, S 50 4TWe highly recommend that you begin by upgrading the variator roller weights before engaging in any performance upgrades. This is the simplest of upgrades and the least expensive. This is a minimal investment and offers a maximum return.The main rule for tuning variators is the lighter the roller the more rpm’s are needed to push the rolls outwards through centrifugal motion to set the gear change in motion. Heavier roller weights need lower rpm’s to start moving.Heavier roller weights = slower take-off speed, more acceleration = higher maximum speed.Lighter roller weights = faster take-off speed, less accerleration = lower achievable speed. The right balance is an individual choice since a scooter racer will want heavier weights to achieve a higher overall s