I tried the Dr. Pulley sliders and did not really get any more top end speed. They do give a smoother, more linear acceleration. They were not really quicker when I verified the performance, but they felt like it. In the end I purchased the Dr. Pulley rollers in the recommended weight for my scooter. IMHO the best solution for over-all performance. Trust me, you are not going to get a substantial return on your investment if you spend a lot of money on after-market performance upgrades. Kymco builds these things pretty much "high performance" from the factory. Just my hard earned two cents worth.