letter tray

Plastic or cardboard trays used to store and transport letter-size mail. Each tray holds 500 to 1000 pieces of mail, depending upon the thickness of the contents. Letter trays are widely used by the U.S. Postal Service, by large-volume mailers, and by recipients of large volumes of mail. flash counts are sometimes done in terms of the number of filled letter trays received from the USPS, giving a quick estimate of the response to a direct-mail promotion. weigh counts are almost always done by letter tray.