Usps Large Flat Rate Box Price 2025. With our free flat rate envelopes, you don’t need to weigh shipments 70 lbs and under. Usps flat rate boxes and envelopes come in various sizes and are available for free at usps offices and online.
With our free flat rate envelopes, you don’t need to weigh shipments 70 lbs and under. Minimum order is 10 boxes.