Kidde 21006406 Interconnectable Wire-In Carbon Monoxide Alarm With Battery Backup, 85 DB At 10 FT Loud, 60 HZ Operating Frequency, 120 VAC Operating, 40 - 100 DEG F Operating, Environmental Conditions: 5 - 95 PCT Relative Humidity (RH), Electrochemical Sensor, Dimensions: 5-3/4 IN Diameter X 1.8 IN