For replacement of existing equipment, security enhanced versions of both horizontal and vertical boxes are now available. They are referred to as “USPS-STD-4B+” boxes and are designed to fit cleanly into buildings with old USPS-STD-4B boxes.
USPS-STD-4B+ boxes are approved for Postal Service mail delivery for indoor installations or protected outdoor locations. However, the Postal Service does not approve the purchase of this equipment for new installations and will not install Arrow locks in any such equipment. You may only order replacement parts for Postal Service-owned equipment that was installed in the past.