4x4 aluminum post sleeve. This 4 in. Read More. . Post sleeves, particularly the Avalon series, are engineered for durability and style. Other options for deck railing posts include composite, PVC and metal posts — such as steel and aluminum deck posts — that stand up to the elements. Weatherables 4x4 Post Sleeve – Weatherproof Premium Outdoor Vinyl Post Cover for Lasting Durability and Easy Installation on Decks, Patios, Porches or Mailbox Posts (4"x4"x96", White) Shop our Post Caps, Post Covers, Fences, Vinyl Decks and Railings including our Westbury Aluminum Support Post - 4" X 4" X 108" Deco Sided (Textured Black). Made in The USA. Simply drop them over your existing posts for an instant upgrade that hides unsightly pressure-treated wood and adds a polished, finished look. x 10 ft. x 4 in.