This Pleasant Hearth Clairmont Fireplace Glass Door reduces heat loss up the chimney by 90-percent when the fireplace is not in use, plus adds style and function. When you"re not enjoying a fire, simply close the smoked tempered safety glass to minimize heat and cool air loss. Fireplace openings 30-Inch to 37-Inch wide and 25 1/2-Inch to 32 1/2-Inch high. For masonry fireplaces only. Not for use on pre-fabricated fireplaces. U.S.A.