Set of 2 Polini springs that reduce pressure by 30% or 8%. The springs press the gear on the rear converter onto the belt. It also creates pressure to shift the variator. A lighter pressure is required once a motor has been tuned to prevent the engine from moving into a dangerously high rev range. The pressure of the springs is closely tied to the variator. If a spring is fitted, it must be matched to the variator. Spring: -8%. Original spring weight: 50/28mm/kg. Polini spring weight: 50/26mm/kg. Spring thickness: 4mm. Total length: 108mm. Internal diameter: 49.5mm. Number of coils: 6. Spring: -30%. Original spring weight: 50/28mm/kg. Polini spring weight: 50/20mm/kg. Spring thickness: 4mm. Total length: 96mm. Internal diameter: 49.5mm. Number of coils: 6.