4 in 1 Mode: This alarm with 4 modes. 1. Timing alarm (sounds 'Di-Di-Di' from 0dB to 108dB if the door remains open for 3/15/30/60s) 2. General alarm (alarm stop if door closed); 3. Constant alarm (constant alarm even door closed); 4. Door Opening Chime (Sounds "DingDong" once door is opened) Loud 108dB Alarm: The door and window alarm helps effectively deter intruders/thieves with a loud 108dB alarm. You can easily set the suitable mode according to your needs.Easy to Install: Simple peel and stick installation, easy to install on most freezer/refrigerator or any door without any tools. package including 2 fridge alarms, 2 magnetic strips, double-sided sticker, user manual. The electronic instruction is on the eighth picture. Installation Note: Be sure to close the alarm and the magnetic strip, the installation distance between them should not exceed 0.78 inch. The 2 parts must be aligned by their alignment arrow. 2 AA batteries can stay for 2 years. (batteries are not included)Widely Used: Magnetic trigger door alarm sensor protecting home through door window entrance and suitable for safe, cabinet, freezers, refrigerators, swimming pool sliding door , store, office, apartment, hotel, etc. Note: The data is all measured manually, please allow 1-3cm error, due to the difference in light and display, there will be some certain color difference, the actual object received shall prevail.