Eliminate the telltale signs that you have an alarm system installed. Unlike conventional magnetic contact switches, these switches are completely hidden. Each of the 10 pairs of Short Round Magnetic Contacts included in this pack are .78 inches long and are ideal on windows and sliding glass doors. The magnet will need 3/4" of material (wood, aluminum, vinyl) around the frame of the window four mounting. Each contact has an operational gap of 3/8 of an inch. Simply drill a 3/8" hole in the edge of a door or window jamb and press fit. The wires are can be passed through the jamb and framing and run over to the alarm system controller. Both the switch and wire are completely invisible when the door or window is closed. Mount the magnet in the door or window so that the two are in contact with each other when the door or window is closed. Other Features The contact switch is waterproof and enclosed in an epoxy compound that is moisture and corrosion resistant. The high-impact plastic case withstands hammering in of the switch and magnet. Comes with 15" of 22AWG wires and handles up to 1 Amp at 10 volts DC. It can reliably operate in temperatures between -15F and 160F. Rated for 50 million openings and closings, this thing will never wear out! Contacts are closed when magnet and sensor are together.