Priority Mail Medium Flat Rate Boxes
Sizes
Inside Dimensions Outside Dimensions
11" x 8-1/2" x 5-1/2" 11-1/4" x 8-3/4" x 6"
13-5/8" x 11-7/8" x 3-3/8" 14" x 12" x 3 1/2"
Features

Priority Mail service offers 2-3 day service to most domestic destinations. Priority Mail Flat Rate boxes are available at many Post Offices and can be ordered online at USPS.com/store. Extra Services, such as Insurance, may be available for an additional fee.

Domestic Prices

Priority Mail Flat Rate boxes are priced low to U.S. destinations, regardless of the actual weight of the piece up to 70 pounds.

Online shipping convenience
Hold For Pickup Service

Under Hold For Pickup Service, Priority Mail items are held at a destination Post Office location for pick up by a specified addressee or designee. Upon arrival of the mailpiece at the destination Post Office pickup location, the addressee will receive an email notification from the Postal Service. At least one of the following extra services must be combined with Hold For Pickup service: Signature Confirmation, or insured mail when the mail is insured for more than $200.

Obtaining Hold For Pickup Service

Online: Complete the online form at USPS.com/pickup

When sealing a Priority Mail Flat Rate envelope or box, the container flaps must be able to close within the normal folds. Tape may be applied to the flaps and seams to reinforce the container; provided the design of the container is not enlarged by opening the sides and the container is not reconstructed in any way.