Mail Boss products can take up to 2 weeks for order processing The In Ground Steel Mounting Post is made of heavy-duty galvanized 10- and 14-gauge galvanized steel with a durable powder-coated finish. Use this 43" in-ground post to mount any Mail Boss locking mailbox. In order for the incoming mail slot of the Mail Boss mailboxes to be within USPS specifications of 41"-45" above the road side surface, the In Ground Post should be buried approximately 12" in ground. This post will fit securely over a 4x4 wooden post for deep installations and reinforcement with rebar.