Greencycle 9PK Door & Window Alarm Sensors — 110dB, 4-in-1 (Alarm/Continuous Alarm/Doorbell/Door-Close Reminder), 3 Modes, Easy Adhesive Install — For Fridge, Dorm, Home, Shop

Compact security sensors from Greencycle that combine four practical functions in one unit: alarm, continuous alarm, doorbell and door-closing reminder. The devices offer three selectable operating modes to match different uses: Continuous Alarm Mode — detects an open door or window and sounds a 10-second alarm; Door-Closing Reminder Mode — triggers three prompt tones when a door changes from closed to open; Doorbell Mode — emits a single prompt tone upon opening. Each unit includes a low-battery warning that sounds automatically when the power is running low, helping avoid unexpected downtime and keeping protection active. The alarm itself reaches 110dB, loud enough to draw attention and deter intruders even in quiet settings. Installation is tool-free: use the supplied double-sided adhesive tape to mount the sensor quickly on doors, windows, freezers, filing cabinets and more — no wiring required. Sold as a 9PK, these alarms are suitable for fridges, dormitories, homes, shops and other indoor spaces.