The RetroFit is an easy to use, easy to install, snap-in replacement mailbox door, for standard 6-1/4 in. wide and 8 in. tall metal mailboxes. The RetroFit simply snaps in and remains secure to fit virtually all standard 6-1/4 in. wide metal mailboxes. Installation takes less than 5 minutes and no tools are required, it simply snaps into place. With the RetroFit, there is no need for grinders and saws to remove the protruding mailbox. It requires no glues to hold in place. The best way to measure to confirm size is the opening of your mailbox canister itself, not the old door. The RetroFit is designed for steel and aluminum mailboxes and does not work on plastic mailboxes. The RetroFit is ideal for broken monument and brick mailboxes where removal of the original mailbox is prohibitive. The RetroFit will also work perfectly on any standard post metal mailbox. The RetroFit is made of rust resistant Aluminum. All metal mailboxes are made with a lip at the front opening where the metal is bent so there are no sharp edges. Our doors have compression wings (one on either side and a small one at the top). These compression wings push in and expand behind that lip holding them into place. We made our doors to match the 3 standard sizes of metal mailboxes so the doors are made to fix each correlating size exactly. The door itself is made to just sit over the top of that front lip like a normal mailbox door. Color: Neutral/Grey.