Kidde HD135F Firex Wire-In Heat Detector With Battery Back Up, Sensitivity: 135 DEG, Heat Sensor, 120 VAC Operating, Audio Alarm, Dimensions: 5 IN Diameter X 2 IN Depth, -20 To 100 DEG F Temperature Range, Environmental Conditions: 5 - 95 PCT Relative Humidity (RH), Mounting: Wall Or Ceiling, 85 DB