USPS Priority Mail Flat Rate tracking works by providing a unique tracking number for each shipment, allowing both the sender and recipient to monitor its progress through the USPS system. This tracking information is updated in real-time as the package moves through different USPS facilities and is scanned at each stage.

Flat rate shipping delivery times vary depending on the carrier and service selected, but generally range from 1 to 5 business days for domestic shipments. USPS Priority Mail Flat Rate is typically 1-3 business days. UPS Simple Rate offers various speeds, including within 5 days, within 3 business days, second day, and next day. FedEx One Rate also provides different delivery speeds, including next day, 2-day, and 3-day options.

USPS offers several types of Flat Rate boxes for Priority Mail, including small, medium, and large sizes, as well as padded and legal flat rate envelopes. These boxes allow you to ship items up to 70 lbs to any state at a flat rate price, regardless of weight or distance within the US.