There are small, medium, and large flat rate boxes; And the bigger the box, the higher the price. The maximum allowed weight is 70 pounds. 2. Pack your items and address your box Pack your items in the USPS flat rate box and address the package. 3. Ship your i...
calculatedShippingRate. packageSize string Optional Applicable values: Large envelope Normal package Large package Very large package USPS Priority Mail Small Flat Rate Box USPS Priority Mail Medium Flat Rate Box USPS Priority Mail Large Flat Rate Box USPS Priority Mail Flat Rate Envelope USPS Priorit...