The smoke detectors were delivered quickly and the supplied battery allowed me the smoke detector to take the off. The DTL. Tone was hard to miss, pointing the the smoke detectors fulfill their function. The betellten combined magnets allowed me a quick installation without drilling or to take a workpiece in the hand. This was very important to me, because I live in a rented apartment and do not want to unnecessarily drill holes. I can the combination smoke detectors and magnets I highly recommend. The price performance ratio is absolutely right in this article.