AX-250PLUS & AX-500PLUS are built to take the worst. With 14kV+ surge security, impact resisting covers, and a beam tolerance of more than 99%, these detectors withstand the harshest environmental conditions. Extra large twin beams protect against false alarms caused by birds, falling leaves, and various other disturbances. These beams come with everything you need for a quality installation process, including Conduit knockouts and a form C relay, as well as optional beam towers, back covers and heaters.