I am fully satisfied with this batch of 3 smoke detectors that work very well. I have installed one in my driveway, 1 in my dining room - living room and the 3rd upstairs on the landing ceiling and not on the walls.
I tested the efficiency by having a stove burn inadvertently it worked very well.
Easy to install with supplied batteries, plugs and screws but can hold with a very good double sided sctoch or "no nails or screws,"