Chapter 11: Postal Standards
GENERAL MAIL CLASSIFICATIONS AND REQUIREMENTS (UNITED STATES)
The United States Postal Service (USPS) offers many types of mailing services, depending on the nature and size of what you are mailing. To check rates and requirements for your mailing, you must first determine whether your piece fits the description of a letter, a large envelope, or a package and whether or not your piece fits within the size requirements for each.
Rectangular card stock mail piece not contained within an envelope.