4-in-1 smart alarm modes: Features timing alert (3/15/30/60s delay), instant alarm (stops when door closes), constant alert mode, and entry chime (DingDong notification). Customize protection for different scenarios. High-security 108dB siren: Magnetic door sensor triggers progressively increasing alarm up to 108dB, effectively deterring intruders and monitoring freezer/fridge door left open accidents. Tool-free installation: Adhesive-backed design with alignment arrows ensures proper magnet contact. Includes 2 alarms, 4 magnetic strips, and dual-sided tape. Compatible with freezers, sliding doors, cabinets, offices, and pool gates. Long-lasting battery efficiency: Low-power design supports 2-year operation with 2 AA batteries (not included). Critical 0.78-inch gap requirement between sensor and magnet for reliable triggering. Multi-surface application: Weather-resistant construction works on metal/wood/glass surfaces. Ideal for commercial refrigeration, retail displays, medical storage, and home security systems.