Dr. Pulley 15x12 Sliding Roller Weights 5.5 Gram Dr. Pulley 15x12 Sliding Roller Weights for Minarelli 50cc 2-stroke engines. Please select weight from drop-down menu. Traditionally, gear ratio is changed by the up-and-down rolling movement of the roller weights in the ramp of the Moveable Drive Pulley (MDF). Now the innovative Dr. Pulley Sliding Roller Weights slide up-and-down the ramp to change the gear ratio. This unique sliding movement (not rolling) provides exclusive advantages to increase CVT performance. With Dr. Pulley, no abnormal w ear will occur even when running in high gear. Dr. Pulley's U.S. Patent Number 7,276,004 states that their sliding roller weights eliminate abnormal wear, prevent reduction gear ratio deterioration, prolong the useful life of the transmission, and have the availability to adjust reduction gear ratios as well as driving performance. At the same time, Dr. Pulley Sliding Roller Weights are also adapted to compensate wear automatically, to adjust by itself to move further outward in a movable drive pulley half and to make the vehicle reach a higher maximum vehicle speed.Please see our Warranty & Returns Policy. Size: 15x12 Set of 6 Available in 3 Gram Through 11 Gram Weights, Including Half Gram Weights Broadens your range of gear ratios Increases acceleration and re-acceleration properties Increases top end speed Lasts longer than standard roller weights U.S. Patent Number: 7,276,004