All items that may be sent as First-Class Mail International (see 241) may be sent in the Priority Mail International flat-rate envelope or small flat-rate box provided the contents are mailable, they fit securely in the envelope or box, and they are entirely confined within the container with the provided adhesive as the means of closure. The flap must close within the prefabricated fold. Tape may be applied to the flap and seams for closure or to reinforce, provided the design of the container is not enlarged by opening the sides and taping or reconstructing the container in any way. Registered Mail service is available. Insurance is not available.