Except for pressure-sensitive filament tape, tapes used for closure and reinforcement should be at least 2 inches wide.Nonreinforced plastic tapes must be at least as strong in the cross direction as in the machine (long) direction.The mailer must comply with applicable postal laws and regulations governing mailability and preparation for mailing, as well as nonpostal laws and regulations on the possession, treatment, transmission, or transfer of particular matter.Information about USPS standards is available from postmasters, business mail entry managers, and the PCSC manager (see Stationery-type items thicker than 1 inch or heavier than 1 pound are not accepted in letter-style envelopes.Paper tape must be at least 60-pound basis weight kraft.The adhesives on gummed tapes must be adequately activated before application and firmly applied with the tape extending at least 3 inches over the adjoining side of the box.Plastic bags must be at least 2 mil thick polyethylene or equivalent for easy loads up to 5 pounds; 4 mil thick for easy loads up to 10 pounds.Heat-shrinkable plastic film—either irradiated polyethylene, linear low-density polyolefin, or copolymer—may be used as packaging for mailpieces under the following conditions only: Cloth bags are acceptable for easy and average loads of up to 10 pounds, if the seams of the bags equal the strength of the basic material.
It is the mailer’s responsibility to refrain from depositing nonmailable matter in the mail.
For easy and average loads of up to 20 pounds, reinforced bags or bags with a minimum of 70-pound basis weight are acceptable.
Nonreinforced loose-fill padded bags are not acceptable as exterior containers, unless the exterior ply is at least 60-pound basis weight.
Mailers must adequately stabilize heavy items within the package.
A strong packaging or paper tape (not cellophane or masking tape) may be used for the closure or reinforcement of packages.