Review on ARDWOLF Photoelectric Smoke Alarm – 2 Pack Fire Alarms | UL Listed, Battery-Operated with Included 9V Battery | 10-Year Life span | Essential for Home Fire Safety by Marvin Short

They were very easy to install as I already had 4 inch fire detectors. I feel safe at night when I see the battery indicator flashing from time to time letting me know the device is working. The battery was easy to install too. There are some alarms/detectors that are so difficult to do that Battery compartment to close , but these detectors are very pleasant. Easy assembly, easy battery replacement, etc.