The Bayshore interior rust sleeve is an easy, quick solution for worn and rusted mailboxes, especially those encased in concrete or brick. It slides into place and fits all manufacturers 6 1/2" x 8" aluminum or steel mailboxes. The base measures 18 1/2" in length. The sleeve provides a moisture barrier and keeps insects out. This sleeve works with the RetroFit door. Please watch the videos for more information.