UL Listed Protectors for areas where abuse to smoke detectors is severe. Patented (D368,670) web-like octagon shape of heavy-duty coated steel wire makes them extremely difficult to break. They are constructed of heavy-duty steel wire with corrosion resistant plastic coating or heavy-duty stainless steel wire. Together, they cover virtually every smoke detector model available. These Steel Web Stoppers are backed by a three year guarantee against breakage in normal use. Installation and servicing are easy with models for both flush and surface mounting. Highly recommended for areas where abuse to smoke detectors is severe