Commercial ALARM SYSTEM Steel Door#2 screw for terminal screwMount Contact Switch with terminals and magnet.Commercial and Industrial SurfaceMount Alarm Reed SwitchWide Gap Surface Mount Contact Switch Screw Mounting  SHAPE  * MERGEFORMAT Operate Gap 2" (50mm) max separation from magnet to switchQuantity: 4 Switches, 4 Magnets4 Sets TotalWhen the magnet is next to the switch,the loop is closed.When the magnet is pulled away the loop opens.4 inches long Grey in color.Reed Switch Specifications Contact Rating: 10W/VA Switching Voltage (Max.) : 200 VDC Switching Current (Max.) : 0.5 Amp. Contact Resistance (Min.) : 150 milli ohms Life Expectancy: 10x 10 6 Operations Insulation Resistance: 10 9 ohms Shock Resistance: 30G for 11mSec. Vibration Resistance: 20G (10 to 1000Hz) Magnets: Rare Earth Plastic Material: ABS PlasticThere maybe a 15% restocking fee when you return the itemIf you have any questions please message BEFORE you buy Alarm Dealers Welcome