This spring offers a 30% increase in tension / pressure compared to the factory fitted spring making it ideal for tuned 50cc engines. When the level of tuning increases, so too should the strength of the springs. Variator roller weights must also be calibrated if torque springs are changed. Original spring weight: 50/20mm/kg. spring weight: 50/26mm/kg. Spring thickness: 4.2mm. Total length: 90mm. Internal diameter: 50mm. Number of coils: 5.