According to Steve's text, on the site, it'll hold 14" slabs of ribs. Unless you are trying to smoke a whole lotta ribs at one time (and I mean a LOT in the #3), I recommend forgetting the rib rack and lay them flat on the shelves, bone-side down. Not only do I think this is the best way to smoke ribs, it's also easier! When they're flat, the meat is insulated from the heat by the bones, and the juices help self-baste the ribs instead of dripping off the end (if they're standing vertical).