DP2M Lens hood?

How does the Sigma hood attach? By bayonet? (I don't have one, so I don't know.)

I've tried rubber hoods on other cameras/lenses, and with some of them the rubber separates from the metal ring which screws into the filter threads. With others, you cannot attach a spring-loaded lens hood. Also, in my experience, rubber hoods entangle themselves with camera cases.

The Sigma hood has an important advantage, in that it is specifically designed for the DP2M lens. It has a rectangular aperture, corresponding to the format of the DP2M. Other generic hoods are compromises; they have round openings which only approximate the angle of view of the lens.