Dr. Pulley 25x17 Sliding Roller Weights Dr. Pulley 25x17 Sliding Roller Weights for the Aprilia Atlantic Sprint 400/500 ('05-'08), Aprilia Scarabeo Light 400/500 ('06-'08), Aprilia Scarabeo 500 ('07-), Piaggio Beverly 400 ('06-'07), Piaggio Beverly Tourer 400 ('08-'09), Piaggio Beverly 500 ('05-'08), Piaggio Beverly Cruiser 500 ('07-'09), Piaggio MP3 400 ('00-'08), Piaggio MP3 LT 400 (2009), Piaggio MP3 Mic 400 ('08-'09), Piaggio MP3 500, Piaggio X Evo 400 ('07-'09), Piaggio X8 400 ('06-'08), Piaggio X9 Evolution ABS 500 ('06-'07) and many more. 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 wear 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 for 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 ve hicle speed.Please see our Warranty & Returns Policy. Size: 25x17 Set of 8 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