This MB Dellorto O ring set can protect your carburettor from the ethanol in modern fuels by changing to Viton O rings. These are Brown to identify them from normal Dellorto rubber items. 
 
This handy kit contains the following items:
 
Carb top O ring (fits PHBL)
Carb top O ring (fits PHBH)
Float bowl O ring (Fits PHBH and PHBL)
Air mixture screw O ring (fits PHBH and PHBL)
Slide stop screw O ring (fits PHBH and PHBL)
Choke jet O ring (fits PHBH and PHBL)
Float bowl main jet holder O ring (fits PHBH and PHBL)