Architectural Mailboxes Grande Post Sand The Grande uses a continuous galvanized steel post section providing strength and durability, even for multiple boxes. The support arms clamp to the post piece at any vertical location to provide flexibility in mailbox height and the cast aluminum base conceals all anchoring hardware. Fully powder coated Post is 3.55 mm (10 gauge) galvanized steel tube Includes all assembly hardware and mounting instructions. (concrete anchors not included)