The 4 in. x 4 in. Post Adapter can be used to attach any Architectural Mailboxes post mount mailbox to a 4 in. x 4 in. wood post. The adapter plate is constructed of heavy gauge galvanized steel and finished with a durable powder coat. 4 in. x4 in. adapter, 4 in. x 4 in. post adapter, adapter for mailbox.