These are hilarious. I bought a six pack of the same model number and two of these because I needed eight total. The six pack works great and are fine. These, however, didn't even have any wire hooking the 9v battery up to the alarm AND the 9v battery area was too small to even hold the battery. Totally ridiculous!!!But the same model in the six pack were all wired correctly and housed the battery correctly. Must be a diff manufacturer for the singles. Caveat Emptor!