Ultra light (3.87kg - 8.53lbs) EN8 steel billet race flywheel for diaphragm clutch NOT-Verto with ring gear for non-pre-engaged starter. Forged is more rigid at high speed. The latest refinement of the Ultra-light Mini flywheel is now made symmetrically to reduce harmonics vibrations caused by earlier versions (those with just 3 large lightening slots), yet it still weighs under 4kg.This is considerably lighter than a safely lightened standard iron flywheel, and also provides a much hardier clutch surface.