I run into the opposite problem, the PO's only carry the flat rate boxes. You see someone come in and want to mail their item PM, it won't fit in the small one, so they have to put it in a $10.70 FRB - well maybe it is just a piece of clothing and only weighs a pound, $10.70 is way too much. If they had a reg. PM box it would go for $6 or so.