priority mail large flat rate box international allows customers to ship large, heavy items at a fixed price regardless of the weight or distance, as long as the contents fit in the box. The cost for USPS Priority Mail Large Flat Rate Box for international shipments is approximately $79.75. This price is consistent for most international destinations, and it includes tracking and delivery within a specified time frame, typically 6-10 business days, depending on the destination country. It is a cost-effective option for shipping bulky items internationally, especially when other shipping methods would be more expensive.