Primo Rib Rack, 5-Slot, for Oval X-Large and Large, Junior, Round

Which Primo grills does the 5-slot rib rack fit?

Four of them: the Oval X-Large, the Oval Large, the Oval Junior and the Round. That is unusually broad for a Primo accessory, most of which are cut for one firebox, and it means the rack follows you if you add a second grill or move to a different size later.

Does it really fit the Round as well as the Ovals?

Yes, the Round is listed in its fit. A rib rack sits on the cooking grate rather than into the firebox, which is why this one can span shapes that most Primo parts cannot. Deflector plates and griddles are the parts where shape genuinely dictates fit.

How many racks of ribs will it hold?

Five slots, so five racks at most, and fewer if you are cooking thick ribs and want air between them. For a family cook or a handful of guests that is usually the right number. For a crowd on an X-Large, the 9-slot version is the one built for volume.

Why not just lay the ribs flat on the grate?

Because they take up far more room that way, and because the underside sits against hot metal while the top gets the smoke. On edge, every rack has air on both faces, the cook is more even, and you free up grate space for everything else you want to put on.

Do I need heat deflectors as well?

For ribs, yes. Ribs want long, low, indirect heat, so the fire needs shielding from the meat with deflector plates sized for your grill. The rib rack solves the space problem; the deflector solves the heat problem, and a rib cook needs both answered.