Original USA double-sided promo flat that was used inside of record stores back when Hounds of Love was first released - it measures slightly over 12” x 12”. This is also one of the oldest promo flats that I own.
The U.S. promo flats tended to be more double-sided than the UK ones. The reversed side of the U.S. flats normally features additional information about the release, so as not to obscure the artwork on the front. In some cases they even featured some really unique artwork that was exclusive to the promo flat only, so it couldn't be found anywhere else. I've got a promo flat for the Mini LP that has some very unique artwork featured on the back, so if I ever manage to unearth it again I'll definitely post it.