Attachment
(1) A letter or other piece of mail placed in an envelope and affixed to the address side of another mailpiece (host piece). The attachment can be of the same mail class as the host or, where permitted, of another class such as an enveloped First-Class Mail piece attached to the outside of a Package Services parcel. The price for the attachment depends on the mail class of the host piece and whether the attachment is incidental to (i.e., closely associated with) the host piece. (2) A ride-along piece attached to an individual copy of Periodicals mail. (3) A repositionable note. (4) Stickers, pressuresensitive release cards, or similar items on the outside of a mailpiece if permitted by mailing standards.