priority mail international flat rate small box is a shipping option provided by USPS that allows customers to send packages internationally at a fixed rate, regardless of weight, as long as the contents fit within the dimensions of the small box. This service is ideal for sending small, lightweight items to other countries, and it includes tracking, insurance, and delivery confirmation. The Priority Mail International Flat Rate Small Box is one of the more affordable ways to ship overseas and is commonly used for e-commerce sellers who need to ship products internationally. The cost is fixed, making it easier to estimate shipping expenses.