ugh, really embarrassing, not sure if anybody knows this, I've looked up and down on the net but I still have no idea how I'm supposed to properly attach the Sto-Fen Omnibounce for the 580EX/580EXII to the 580EXII. The included documentation said to pull it apart on the long side as in break it??
The diffuser simply pushes on over the end of the flash. The fit on the 580 II is almost too tight, but it seems to loosen slightly over time, as the soft plastic stretches.