Review on FIRST ALERT BRK CO5120BN: Reliable Hardwired Carbon Monoxide (CO) Detector with Battery Backup in White by Terrance Haralson

I ordered 4 of these carbon monoxide alarms, the exact ones I replaced so I didn't have to change the base or rewire. You need a flat screwdriver to separate the plugs, after which the new one is inserted with a little pressure. Some people complained that it was difficult to attach the round block to the base, it kept sliding down. The trick is to slide the wires up and out of the way. When installing on the base, first rotate the bottom counterclockwise a little to lock the grooves, then rotate clockwise and it should lock. I like that it comes with a Duracell battery and not a cheap battery. My last carbon monoxide detectors lasted about 7-8 years before I started hearing 5 beeps.