Foil-Face FlexWrap insulation is a ceramic fiber blanket covered with 3 mil thick foil. It is made with special ceramic fibers that that resist separation, making it perfect for flue liner installations with bends and offsets. It also helps to center your liner properly in the chimney. One wrap of 1/2" Foil-Face FlexWrap insulation meets the UL 1777 zero clearance listing. Measures 1/2" x 24" x 25'. Shipping is FREE (contiguous US only).