This is a billet aluminum Brembo master cylinder cap, the large size fits all bevel drive twins front Brembo master cylinders (Darmah, 900SS, GT, GTS, Sport), the small size fits all bevel drive twins rear Brembo master cylinders (Darmah, 900SS).
Please note that this does not come with a bellows. Use your own one or buy a bellows kit from us along with yoru cap.