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. 5-1/8″w x 7-1/8″h outside flange dimensions. 4″w x 5/8″d x 5-15/16″h return flange dimensions.