The square format of the stamp was developed in partnership with the greeting card industry specifically for oversized or square envelopes. These envelopes cannot pass through the automated Postal processing system and have to be hand-cancelled. They are charged a non-machineable surcharge even if they weigh less than one ounce. Greeting card envelopes printed with a silhouette of a butterfly indicate the need for additional postage or the use of a butterfly stamp. Any non-machineable envelope, like oddly shaped or vertical envelopes, as well as lumpy envelopes, rigid envelopes, or mail with clasps, ribbons, or buttons, may use this stamp.

Stamps ordered. Now I just need to figure out, 1-2-3-4-5 chips postage and I'm ready for a wild eBay sale.