These steel cages help protect the vital sensor units of projected beam type smoke detectors. They are protected in large areas such as gymnasiums, warehouses and auditoriums. The STI Beam Smoke Damage Stopper is designed to protect both transmitter and receiver sensors. This device is constructed with super tough 9-gauge coated steel wire. The guards are extremely difficult to break. This device is coated with a tough, corrosion resistant polyester shell. The installation process is simple and quick with anchors and screws provided.