I actually bought two packs of these wire grids.  The first pack I used to make a guinea pig cage that was 2 x 4 with a 2 x 1 loft.  The second pack I use as a fold away exercise run.  They are great value and even with one pack you can make a cage that is bigger than shop bought cages and for a fraction of the price.  I'm sure they make good shelves too!