HTRolls are made with CPT with a specific formula and their weight is marked on one side. HTRolls represent a technical spare part for the original one, in a complete series of calibrated elements capable of varying your scooter's transmission ratio and perfectly regulating its speed and acceleration. Operation Due to the rotation, the weight of the rollers becomes a centrifugal force; the higher the rollers weight, the lower the gear change time, and vice-versa. Variator calibration To optimize engine's performance, select rollers that in operation, maintain the engine at the highest power regime. By diminishing the rollers weight the engine s RPM increases; on the contrary, by increasing the rollers weight the RPM decreases. Compatible with: - Aprilia: Scarabeo 50 Piaggio_S, SR 50 04-Piag._S - Gilera: DNA 50 LC_S, Runner SP 50 -05_S, Runner SP 50 06-_S, Stalker 50 AC_S, Thyphoon 50 AC_S - Piaggio: Beverly 50 06-_S, Liberty 50_S, NRG 50_S, ZIP SP 01-_S