Here is an excellent bargain The 20 gram 20×15 DrDescription Here is an excellent bargain. The 20 gram 20×15 Dr. Pulley sliding roller weight is priced to sell. But if you want this pack of six roller weights you had better act fast.Traditionally, the gear ratio in scooter CVTs is changed by the in-and-out rolling movement of the roller weights. With the innovative Dr. Pulley sliding roller weights, the roller weights ??slide?? inward and outward in the Movable Drive Pulley (MDF) to change/extend the gear ratio. WARNING California Residents: Proposition 65 Warning Specifications Size: 20x15Weights: 20g.