Only a perfectly balanced scooter can transfer all its power to the road. If poorly tuned, the scooter quickly loses up to 30% of its engine power. So hundreds of pounds of high end tuning parts are often wasted as only a mildly sporty tune gets to the road. The art of scooter tuning is not only about quality products, but rather coordinating these into a neat little package. Variator Rollers: 6 rolls 19x17mm, each @ 8.7 g weight.