Protective deviceThis is a set of magnetic sensing switches used to protect doors and windows. A protection device monitors the opening and closing of doors and windows. Magnetic Contact Garage DoorYeuri High quality magnetic sensor contacts with strong magnetic sensitivity, sensitive and long life life. Magnetic contact detectorEasy to install. The wired part is often installed on the fixed door frame and the corresponding part is mounted in the corresponding location on the door. Simple to install, no hassle. Use widelyIdeal entryway warning for homes, apartments, mobile homes, dorms, offices, hotel rooms, garages, etc. . Aluminum alloy, wear-resistant, not easy to rust, light and practical Waterproof, rainproof and safer Note: Cannot be used alone. Should work with main unit of alarm system for alarm. Features: Detection distance: 50~70mm / 1.9~2.7in Package included: 1 * set of magnetic detection contacts