Enhance your home security system using these magnetic contact security sensors to safeguard your home's doors and windows. The Surface Mount Miniature Contact Switch is half the size of standard magnetic contacts, making them perfect for discretely hiding behind window and door frames. In addition to windows and doors, these small contacts are ideal for alarming safes, gun cabinets, jewelry boxes, china cabinets, or just about anything that opens and closes.Compatible with most standard, hardwired alarm systems. They stick on with supplied self-adhesive tape, or can be screwed down. Contacts are closed when magnet and sensor are together.