€¢ High-density polystyrene construction €¢ For sidewall or ceiling applications €¢ 1/3 in spaced fins set at 20 deg angle €¢ 3/16 in margin turnback €¢ Rust proof and scratch resistant >> Return air grilles sidewall polystyrene white finish size 6 in x 12 High density polystyrene construction. Rust proof and scratch resistant rounded corners for safety. 3/16 in margin turnback. High-density polystyrene construction. Rustproof and scratch-resistant rounded corners for safety. 3/16 in margin turnback. High-density polystyrene construction. Rust proof and scratch resistant rounded corners for safety. 3/16 in margin turnback."