JJC LH-S401 bayonet Lens hood is designed for SIGMA DP2 Quattro Camera. Lens hoods are primarily designed to prevent unwanted stray light from entering the lens by extending and shading the end of the lens. In addition, since the end of the lens is extended, you also get the added benefit of some extra protection from accidental impact.  The hood is also reversible to stay on lens when not in use. Now the original SIGMA lens cap can be attached to the lens normally. JJC LH-S401 Lens hood replaces SIGMA LH4-01 lens hood.

Product highlights
Prevents unwanted stray light from entering the lens
Extra protection from accidental impact
Will not affect the use of a filter 
Reversible to stay on lens
Compatible with the original SIGMA lens cap