the plastic access panel is designed to provide easy access to walls & ceilings. The high impact styrene plastic with u.v. Stabilizers will not fade or corrode. All units except the 14×29 are hinged with a removable door panel feature. White finish. 5-7/8″w x 8-7/8″h outside flange dimensions. 6-1/4″w x 9-1/4″d x 3/4″h return flange dimensions.