Glixal ATKS-04016 18x14mm High Performance Racing Variator Roller Weights Set 152QMI 157QMJ GY6 125cc 150cc Scooter Moped ATV Go-Kart (8 gram) Size: 18x14mm Weight:8g 6pcs/Set Material: High wear-resistant nylon Heavier roller weights= A slower take off speed and a higher top speed. Lighter roller weights = A faster take off speed and lower top speed. Please Note: The exact performance of upgrade parts will be affected by many other factors