Replacement Mineral Wool (050-721) from Original Equipment Manufacturer (OEM) replacement part is an Original Equipment Manufacturer (OEM) replacement part that is compatible with a variety of Hearth & Home Technologies fireplaces and stoves. It is used to insulate the firebox and prevent heat loss. The mineral wool is made of a high-quality, fire-resistant material that will not melt or burn. It is easy to install and will help to keep your hearth product running efficiently and safely. It is important to check the compatibility of this product with your specific hearth product before ordering; please consult the owner's manual.