Well, the Home Depot people didn't really know what I was asking about - but once I told them I was looking for it where the packing boxes are kept, they led me right to that area. It's a long flat box, the sheets are folded into thirds, so it's a long thin box that hold 145 sheets, probably about yay high (I know you can't see my fingers - so about 4 inches tall).
I understand that Lowes also carries it.