Salsbury 3500 Series Vertical Mailboxes - Recessed Mounted - U.S.P.S. Access. Vertical mailboxes are U.S.P.S. approved for replacement and/or retrofit installations. Manufactured by Salsbury Industries to USPS-STD-4B+ Specifications. Ideal for apartments, condominiums and commercial buildings. Made entirely of aluminum. Feature a durable powder coated finish available in aluminum, brass, bronze, sandstone and green. Rough opening for recessed mounted vertical mailboxes is 1-1/2" less than the unit"s width, 1-1/4" less than the unit"s height and equal to the unit"s depth. Fits into a rough opening and secured with mounting hardware (not included) through the back or side panels. Units include a fully integrated flanged collar which fits over the rough opening. Individual compartment size is 5-1/2" W x 16-1/4" H x 6-3/4" D. Salsbury Industries is an ISO 9001: 2008 certified company and has excelled in the field of manufacturing since 1936.