Ideal for settings with limited wall depth; this USPS Approved solution provides greater flexibility in mailbox placement and installation. Designed for indoor or outdoor use; this heavy-duty STD-4C mailbox enclosure allows standard modules to quickly and easily be mounted to any flat surface. The easy-to-assemble collar has an industry exclusive slotted back design for ease in installation and reduction of overall unit weight. This 4C module is not approved for Postal delivery as it cannot be mounted to adhere to all USPS installation regulations.