Managed mail tray and sleeve
Currently in use at the U.S. Postal Service, the managed mail (MM) tray and sleeve are constructed of 3/16 inch corrugated fiberboard. Their combined tare weight is 1.8 pounds. Full trays accommodate an average of 600 First Class or 450 bulk business letters, which include letters pre-sorted by business mailers. The tray is marked "Label Other End" and "U.S. Mail". The sleeve is marked on top with the U.S. Postal Service logo and on the sides with "Property of U.S. Postal Service."
The USPS designed MM trays and sleeves to provide a more efficient means of dispatching letter-size mail. Although these trays have a relatively short service life (up to 20 uses), they are much lighter than plastic trays, which saves in mail transportation costs, especially air transport.
The corrugated cardboard tray (1984.0693.2.1) is used in tandem with the managed mail tray sleeve (1984.0693.2.2) to handle large volume mailings. The tray slides into the sleeve, which protects the mail and makes the units stackable. Letter trays that will travel by contract carrier (as opposed to USPS owned transportation) are sleeved, and then a single plastic strap is placed lengthwise around the tray and sleeve to provide security. Trays transported by USPS transportation are not strapped.