How big is a priority mail flat rate envelope

According to the United States Postal Service (USPS), a Priority Mail Flat Rate Envelope is a rectangular envelope that measures:

This envelope is designed to be a standard size that can be easily processed and handled by the USPS. It's a great option for sending lightweight items, such as documents, letters, and small packages, as it provides a flat rate shipping cost regardless of the weight of the contents.

Here are some additional details about the Priority Mail Flat Rate Envelope:

Keep in mind that these dimensions and weight limits may be subject to change, so it's always a good idea to check the USPS website for the most up-to-date information.