Check the listing for details. 5 Magnet 5/8 Round Hole Disc Doughnut WINDOW SENSOR CONTACT Rare Earth Neodymium. Condition: New. Listed at 17.00 USD. This listing is for 5 rare earth magnets.5/8-inch-wide (round) 3mm inner hole, one side is flat the other side is countersunk for flush mounting of screws.To upgrade your alarm system, whether home or business, use these replacement magnets for a security connection contact or sensor, which offers a wider operating gap and in turn less false alarms. Extra strong for crafts, or holding holiday items, or signs, on metal doors. (may need multiple magnets depending on the weight of the item, and how much steel is in the door)Replace Wired Door or Window Sensors Detector for Burglar Alarm with a single screw or double stick tape, not included.The rare earth magnets are some of the strongest magnets available, although strong they are brittle. Do not drop, or clink together as they can fracture, this includes over tightening with a screw. Message with questions BEFORE you purchase. Alarm Dealers are Welcome