Needed to replace 5 “life expired” smoke detectors and 1 “ heat detector. Found an appropriate replacement which could fit straight into our existing bases. Ordered over the weekend and duly delivered mid afternoon on Tuesday. Replaced all 6 and tested within an hour. Price was excellent. Only gripe I had was perhaps overzealous application of the tape that binded my batch together. The 2 on top had plastic guides broken. This didn’t affect what I was doing as the bases previously installed were intact. But maybe quiet word with the packet please 🙂. The base and detector are separated (one resting on top of the other) so any “squeezing of the box may break the guide. Still get 10/10 😃