Universal Stopper® Fire Alarm Covers, SurfaceUnique and patented device helps stop false alarms, without restricting legitimate alarms When cover is lifted it sounds a piercing 105 dB warning, drawing attention to the area or pranksters Horn will sound until cover is snapped back onto the frame (or for the life of the battery) High strength piano hinge Clear, tamperproof, tough polycarbonate shield and frame fit over pull station or call point UV stabilized covers are for indoor or outdoor use