Dr. Pulley Sliding Roller Weights 17x12 (5g) Size: 17x12, Set of 6 Fits Aprilia SR50 & SR Di Tech, Derbi Atlantis, Italjet Formula Lc, Malaguti Ciak and many more. Increases acceleration and re-acceleration properties Broadens your range of gear ratios; Increases top end speed Lasts longer than standard roller weights