RD flank steak ?

For a tailgate this yr I'll be cooking a flank steak fajita & saw that my local RD sells them but they're 5+lb range vs the 2+lb I see at my local grocery stores. What is the diff in what I'm getting at RD? Is it just a larger steak or is it a 2 pack? It will be a large crowd I'll be cooking for so trying to figure out what I'm getting at RD vs local grocery store to figure out logistics of the cook on the meat.