In 2004, the United States Postal Service redefined and renamed the classes of mail. Fourth Class Mail was split into several categories including Library Mail, Bound Printed Matter, Media Mail and Parcel Select.

Library Mail

Library Mail is used to send items between educational organizations and museums. Some other organizations may qualify for Library Mail if approved by the Postal Service. According to the USPS, "Content is limited to books, sound recordings, academic theses, and certain other items."

Mailers can add services to Library Mail, including delivery confirmation, signature confirmation, insurance, collection on delivery, return receipt and restricted delivery.

The return address must show the name of the organization or institution the mailer is associated with.

Bound Printed Matter

According to the USPS, "Bound Printed Matter service is a cost efficient way to mail permanently bound sheets of advertising, promotional, directory or editorial material such as catalogs and phone books."

Bound Printed Matter (BPM) can be mailed by imprint only, meaning that mailers must have a bulk mail account with the USPS. BPM can weigh up to 15 pounds, and rates are determined by weight, distance and shape.

Media Mail

The USPS describes Media Mail service as, "A cost efficient way to mail books, sound recordings, recorded video tapes, printed music, and recorded computer-readable media (such as CDs, DVDs, and diskettes." Items shipped at the Media Mail rate can have additional services added, including delivery confirmation, cignature confirmation, insurance and collection on delivery.

Media Mail can weigh up to 70 pounds, and rates are determined by weight, distance and shape.

Parcel Select

Parcel Select service is used by large and medium-size shippers for economical delivery of parcels. Mailers save money by mailing their items from locations closer to the destination. The USPS offers three levels of entry for Parcel Select service.

Parcel Select service from the USPS offers a variety of options including:

Additional services for Parcel Select include delivery confirmation, signature confirmation, insurance, collection on delivery, return receipt and restricted delivery.

Parcel Post

Parcel Post is the most affordable choice for mailers sending items that do not qualify for Library Mail, Media Mail or BPM. Parcels can weigh a maximum of 70 pounds and measure up to 130 inches in length and girth combined.

Items shipped at the Parcel Post rate can have additional services added, including delivery confirmation, signature confirmation, insurance and collection on delivery.