Dr. Pulley 18x14 Sliding Roller Weights 9 Gram Dr. Pulley 18x14 Sliding Roller Weights for 125/150cc 4-stroke GY6 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 we ar will occur even when running in high gear.Please see our Warranty & Returns Policy. Size: 18x14 Set of 6 Choose From 7 Gram Through 17.5 Gram Sizes 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