Federal regulations at 27 CFR § 555.109 require that you mark all explosive materials imported for sale or distribution. You need not mark those materials imported for your own use. However, the fact that the structure of your operations makes it difficult to distinguish materials imported for sale from those imported for your own use may make it practical for you to mark all of the imported display fireworks. Bear in mind that any materials to be sold or distributed must be marked within 15 days after release from U.S. Customs custody. Therefore, those materials not marked within 15 days may not be later marked and sold or otherwise distributed.