Check the listing for details. Wired Surface Mounted NC Magnetic Door Window Contact Sensor Alarm Switch 5 Pack. Condition: New. Listed at 10.12 USD. Wired Surface Mounted NC Magnetic Door Window Contact Sensor Alarm Switch 5 Pack Product Information: Product name: Surface-mounted Magnetic Door Switch, Type: MC-31, Color: White, Material: PlasticSpecification: Contact Type: NC, Hole Dia.: 5.8mm, Actuation Distance: 8mm±18mmSizes: 64*12.*12mm and 64*20*12mm（L * W * H),pack of 5 with 20 screws.NC Type: NC means normally closed. If the magnet is closed to this switch, the signal is conductive, otherwise, if the magnet is far away from this switch, the signal is disconnected.Applications: It is suitable for magnetic windows, doors, cabinets etc. Ideal for door, window security. (n/a) Number of Items 5 Mounting Type Door Mount Switch Type Magnetic Reed Switch Material Plastic Connector Type Screws Terminal Screw Operation Mode automatic Actuator Type Magnetic Contact Type Normally Closed Contact Material Plastic Number of Positions 2 Size MC-31