Make a strong statement with our Westhaven post-and-beam style 4″ x 4″ aluminum square Mailbox post systems. Mailbox post system features a durable, low maintenance powder coat finish that will look great for years and comes with a Lewiston Cast Aluminum Mailbox, three cast aluminum address plates, support bracket, decorative finial and square collar. Westhaven Mailbox Collection is made of rust-free cast aluminum with a durable weather resistant finish. Three Cast aluminum personalized address plates with Gold Numbers. Post mounts directly into ground, mailbox interior dimensions 7 x 6.5 x 18.