Salsbury 4800 Series Heavy Duty Rural Mailboxes are U. S. P. S. approved. Manufactured by Salsbury Industries to USPS-STD-7B specifications. Made entirely of aluminum. Constructed of a 1/8" thick extruded aluminum body with a 1/8" thick die cast aluminum front door and rear cover. The die cast door is attached to the body with a full-width stainless steel hinge allowing for smooth operation. Salsbury Industries is an ISO 9001: 2008 certified company and has excelled in the field of manufacturing since 1936.