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 Jose Mcdaniel

I haven't tested them so I can't comment on their characteristics, but I was very impressed with the compact design and ease of installation. As far as there is a feature that prevents the detector from being installed (attached to a wall mount) when the battery is not installed, preventing people from removing a dead, beeping battery and simply reinstalling a useless device. Comes with a quality 10-year lithium battery and drywall anchors. I will buy more.