The Dry Rib fastens onto one shoulder strap with two fasteners, on the webbing below the padding. There is also another fastener that attaches to the opposite shoulder strap that has some webbing that attaches to the Dry Rib via a quick release buckle. If you get one, make sure to take the webbing out of the two fasteners on the same side. The way it ships makes it look impossible to put on.

If you're having trouble visualizing that, or I did a poor job of describing it, picture a fanny pack with one end of the actual fanny pack attached to one should strap below the padding, and the belt of the fanny pack attached to the other shoulder strap below the padding (with the quick release buckle somewhere near the very bottom of your your sternum).


As far as size, I carry a Canon 20D (without grip), with a Canon 17-55 f/2.8 IS mounted on it with the hood reversed, an Op-Tech strap and filter case, with an extra battery and CF case in a Dry Rib. I could fit a lens with a little more length to it (easily 1 more inch, maybe 2 inches longer), but it might be tight to squeeze a second lens in there. A full-size body with vertical shutter release might also be a little tight, especially depending on how large of a lens. The Dry Rib is not padded, so it can take the form of whatever you're putting in there, but I think you'd need a smaller lens (Canon 50/1.4 or something similiar) if you wanted a pro-size body to fit in there with a lens mounted.


Another option if you need to carry a second lens could be the Wet Rib. AFAIK it's a Dry Rib with a water bottle holder (aka second lens holder).

Both the Dry Rib And Wet Rib look to be available at Moosejaw.