The Priority Mail flat rate boxes carry the most variety in size: from small windowed envelopes to large envelopes for legal documents, and small, medium and large boxes in side-loading and top ...

11″ x 8-1/2″ x 5-1/2″ Inside11-1/4″ x 8-3/4″ x 6″ Outside 13-5/8″ x 11-7/8″ x 3-3/8″ Inside14″ x 12″ x 3-1/2″ Outside $19.30 $19.91 Large Flat Rate Box; 11-3/4” x 12″ x ...

The postal service charges $17.10 to deliver a medium-size flat-rate box anywhere in the U.S. and $22.80 to deliver the large size, which is about 50 % bigger. The maximum weight for either box at ...

WASHINGTON — The Postal Service is adding a larger flat-rate Priority Mail box and a charge for Sunday and holiday delivery, the first changes it has made under a law approved last year ...