This Pleasant Hearth Carlisle Fireplace Glass Door reduces heat loss up the chimney by 90% when the fireplace is not in use, plus add style and function. When you're not enjoying a fire, simply close the clear tempered safety glass to minimize heat and cool air loss. This handsome accessory features a high-temperature classic black powder-coated finish and easy-grip 5in. door handles. Fits masonry fireplace openings 36in. to 43in. wide and 25 1/2in. to 32 1/2in. high. For masonry fireplaces only. Not for use on pre-fabricated fireplaces. U.S.A.