USPS Priority Mail Flat Rate boxes are easy-to-use. You can easily be shipping like just know the USPS tracking Flat Rate box sizes, prices, and how it works before you buy. Priority Mail Flat Rate shipping service will take 1 to 3 days provided by the U.S. Postal Service tracking features one flat rate for delivery of a package or envelope to its destination.
You can Track packages and shipments using U.S.P.S Tracking
USPS Tracking service allows a maximum weight of 70 lbs for each envelope or package. Priority Mail Flat Rate includes free shipping supplies available at the Post Office or sent directly to your residence for no charge.