For added protection around your home, add a pair of Surface Mount Magnetic Contact Switches to almost any security system. There are 10 pairs of switches included in this kit allowing you to monitor multiple areas around your home. These switches are ideal for any normally open location and will send an alert signal to your security system when it is no longer in a normally open state. Simply mount the magnetic sensors on a door or window so that the two are in contact with each other when the door or window is open. Slotted mounting holes make it easy to adjust the distance between the magnet and the sensor, with a maximum operational gap of 3/4". Measuring 2.48" long and half an inch high, they can be attached with wood or sheet metal screws, sold separately. Other Features The switch is waterproof and mounted in a high-impact plastic case. The rhodium plated contacts handles up to 100mA at 100 volts DC and are rated for 50 million openings and closings. It can reliably operate in temperatures between -15F and 160F. The sensor's maximum operational gap is 3/4".