Duct tape, sometimes called duck tape, is cloth- or scrim-backed pressure-sensitive tape, often coated with polyethylene. There are a variety of constructions using different backings and adhesives. One variation is black gaffer tape, which is designed to be non-reflective and cleanly removed, unlike standard duct tape. Another variation is heat-resistant foil (not cloth) duct tape useful for sealing heating and cooling ducts, produced because standard duct tape fails quickly when used on heating ducts. Duct tape is generally silvery gray, but also available in other colors and even printed designs.