USPS Packaging Instruction 4A

Flammable Solids

A flammable solid that qualifies as a Limited Quantity surface material is permitted in the domestic mail via surface transportation only, provided all applicable requirements in 344 are met.

Proper Shipping Name

• Various (see Appendix A).

ID Number

• Various (see Appendix A).

Mailability

• International Mail: Prohibited.
• Domestic Mail: Permitted only via surface transportation.

Required Packaging

Primary Receptacle

• The primary receptacle must have a secure seal and together with its contents must not exceed a weight of 1 pound.
• Multiple primary receptacles are permitted.

Cushioning Material

• Sufficient cushioning material must be used to absorb shock and the primary receptacle from breakage.

Outer Packaging

• Strong outer packaging that is capable of firmly and securely holding the primary receptacle and cushioning material is required.
• Each mailpiece must not exceed a total weight of 25 pounds.

Marking

Labels and markings must be placed on the address side of the mailpiece unless specified differently in 221.1 and 325.1.

• The outer packaging must bear an approved DOT Limited Quantity surface mark designating surface transportation, prepared under 344.3a.
• A complete return and delivery address must be used.