With the 2 aforementioned Kidde smoke alarms, I did not want to break my reinforced concrete ceiling. So I went searching on Amazon an alternative: adhesive bonding and loving. There, I fell on the response of Julien, who had the same type of smoke detector as me. Well thank you, Julian! Then vendor Bargain24 on Amazon Marketplace proposed a pack of 2 fasteners at a price that suited me fine. So I ordered home. The seller immediately proceeded to sending my order, and made me arrive simultaneously by email detailed instructions fixings. So I knew in advance exactly how. Excellent from the seller! And finally, the icing on the cake, with the multitude of comments about smoke detectors, I do not know if it yourselfers Sunday or fakes, but some comments are really hilarious!