Usually, the gear ratio in scooter CVTs is changed by the in-and-out rolling movement of the roller weights With the innovative Dr Description Usually, 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. Specifications Size: 19×17 Available Weights: 8.5g, 9.0g, 9.5g, 10.0g, 10.5g, 11.0g, 11.5g