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2 Containers

2-1 General

Several types of containers are acceptable for mailing items if the containers and items are prepared within the standards of this publication. The principal types of mailing containers include the following:

• Bags, bales, bundles, films, and wraps.

• Boxes.

• Cans and drums.

• Envelopes.

• Tubes.

2-2 Bags, Bales, Bundles, Films, and Wraps

2-2.1 Use

Bags, bales, bundles, films, and wraps are acceptable for mailing certain easy loads and average loads. The contents in these containers should be compressed when possible. The Postal Service does not accept such containers for the mailing of difficult loads.

2-2.2 Paper Bags and Wraps

2-2.2.1 Easy Load up to 5 Pounds

A paper bag or paper wrap is acceptable. The paper must be of at least 50-pound basis weight - the strength of a regular large grocery sack. The contents must be immune from impact or pressure damage. The combining (layering) of several sheets that add up to or exceed a 50-pound basis weight is not acceptable.

2-2.2.2 Easy or Average Load up to 20 Pounds

A reinforced bag or a bag of at least 70-pound basis weight is acceptable. A nonreinforced loose-fill padded bag is not acceptable as an exterior container unless the exterior layer is of at least 60-pound basis weight.

2-2.3 Plastic Bags and Films

2-2.3.1 Plastic Bags

A plastic bag - polyethylene or equivalent - used as a mailing container for an easy load must be stretchable, must resist puncturing, must be relatively leak-proof, and must have the following strength requirements:

• For up to 5 pounds, at least 2 mils thick.

• For up to 10 pounds, at least 4 mils thick.

2-2.3.2 Plastic Films

Heat-shrinkable plastic film - copolymer, irradiated polyethylene, or linear low-density polyolefin - used to form an outer mailing container must meet the following requirements, based on load type and weight restriction:

• For an easy load of up to 5 pounds, at least 3/4 mil thick.

• For an average load of up to 5 pounds, at least 1-1/4 mils thick.

2-2.4 Cloth Bags

For an easy load or an average load of up to 10 pounds, a cloth bag is acceptable if its seams are as strong as the basic material forming the bag.

2-2.5 Bales and Bundles

If it is within postal weight limits, a bale or bundle - a large bound or wrapped package of flat materials - is acceptable if it is adequately compressed and reinforced to contain the contents.

2-3 Boxes

2-3.1 Use and Type

2-3.1.1 Paperboard

A paperboard box (similar to a suit box) is acceptable only for easy and average loads of up to 10 pounds.

2-3.1.2 Metal-Stayed Paperboard

A metal-stayed or stapled paperboard box is acceptable only for easy and average loads of up to 20 pounds.

2-3.1.3 Solid and Corrugated Fiberboard

A solid and corrugated fiberboard box is acceptable for all load types up to the weight and size limits shown in Exhibit 2-3.1.3, unless otherwise specified. The box grade (bursting strength) of a box is printed within the circular or rectangular boxmaker's certificate (pictured here), which lists the box's maximum size and gross weight limits for easy and average loads. The first maximum limit reached for an item to be mailed, whether size or weight, governs the grade of box to be used.

Exhibit 2-3.1.3

2-3.1.4 Wood, Metal, or Plastic

A wood, metal, or plastic box is acceptable for all load types. The box's acceptability depends on its construction, its ability to withstand shock and pressure, and its potential to damage other items.

2-3.2 Size

A box used as a mailing container must be large enough to hold the items and any surrounding interior cushioning material. If the box is too large and the items inside the box are inadequately blocked or cushioned, the items might shift in transit. If the box is too small, the cushioning might be ineffective protection. In either case, the box or items might get damaged during handling and mail processing.

2-3.3 Making Boxes

If a box of the size required for an item is unavailable, other boxes can be resized. Exhibit 2-3.3 shows how to cut a larger box down to the needed size and how to make an acceptable mailing container from two boxes of the same general dimensions by removing their flaps.

Exhibit 2-3.3

2-3.4 Banding

A box containing a difficult load must be reinforced with banding (strapping). The box should be banded about every 8 inches in two directions around the box. See 4-3 for more details on banding.

2-3.5 Outer Wrapping

If a box itself is adequate for mailing, wrapping paper should not be used to cover the box. If wrapping paper is necessary, paper as strong as a regular large grocery bag (60-pound basis weight) is recommended. The appropriate type of tape should be used to close and reinforce the box. See 4-5 for more details on selecting and using tape for closing and reinforcing packages.

2-4 Cans and Drums

A can or drum with positive closures (clips, soldered tops, screw-on caps) is acceptable for mailing certain items such as liquids or powders. Generally, a can or drum with only friction closures (push-down types) is not acceptable. Protruding devices (such as locking rings) must be shielded or covered with padding to prevent injury to Postal Service employees or damage to other mail or mail processing equipment.

2-5 Envelopes

2-5.1 Use

Envelopes are acceptable for mailing certain items that can reasonably be expected to be processed and delivered without damage to the contents or to other mail or mail processing equipment.

2-5.2 Letter-Style Envelopes

A letter-style envelope is any nongusseted envelope within the dimensions shown in Exhibit 2-5.2. A letter envelope is acceptable for mailing nonrigid stationery and similar items weighing up to 1 pound and measuring up to
1 inch thick.

Exhibit 2-5.2

2-5.3 Other Envelope Styles

For an easy load of up to 5 pounds, an envelope that exceeds the letter-size dimensions is acceptable for mailing. This large envelope should be made from paper of at least 28-pound basis weight or from material with a Mullen strength greater than 90 pounds per square inch.

An envelope designed as a photographic film mailer or a gusseted envelope is also acceptable for mailing if it is made from envelope paper of at least 24-pound basis weight.

2-5.4 Odd-Shaped Items

Pens, bottle caps, and similar odd-shaped items are not acceptable in a letter-sized envelope mailed at the single-piece First-Class Mail rate. These items can split or burst the envelope and injure Postal Service employees or damage other mail and mail processing equipment.

An envelope may be used to mail an odd-shaped item at the bulk Standard Mail rate if the item meets the requirements for that mail class. The item should be wrapped with the other contents of the envelope to streamline the shape of the envelope for automated processing. The item's package should be able to effectively hold it so that the contents and the package will not be damaged.

2-6 Tubes

A fiberboard tube or similar long container is acceptable for mailing items if the tube length does not exceed 10 times the girth (the distance around the thickest part of the container). As a minimum, the strength of the tube ends must equal the tube sidewall strength, unless the contents are lightweight rolled items such as maps or blueprints. In any case, the sidewall strength must equal the thickness of the fiberboard, as shown in Exhibit 2-6.

Crimped or taped-end closures are not acceptable for mailing items other than lightweight rolled material. Tape must completely encircle the seams on friction slide closures of mailing tubes.

Exhibit 2-6