Assembling the smoke alarm without drilling, screwing or noise.No damage to the roof or cables / ducts.Very easy and fast assembly with two self-adhesive magnetic plates.Easy smoke alarm removal (for tests, battery replacement, etc.).Not suitable for vinyl, styrofoam, non-stick coating, silicone or Teflon coated wallpapers. Suitable only for smoke alarms with a diameter of less than 8 cm.