High Quality race clutch from Malossi. You can adjust the rpm at which the clutch engages by increasing the spring preload. You need a bit of manual dexterity for this, though.
ATTENTION! Since 98, Minarelli engines (Aprilia, Yamaha) come with new clutches. Please check whether your clutch has two or three shoes. As an alternative, you can measure the inner diameter of the clutch bell, which should be 105mm (2-shoe-clutch) or 107mm (3-shoe-clutch).