Kidde 1279-9999 Hardwire Interconnectable Smoke Alarm With Battery Backup, 85 DB At 10 FT Loud, 120 VAC Operating, 40 - 100 DEG F Operating, Environmental Conditions: Up To 85 PCT Relative Humidity (RH), Ionization Sensor, Dimensions: 5-3/4 IN Diameter X 1-1/4 IN Depth, LED Display, Mounting: Wall O