Size: 5" Wide X 3-1/4" TallPlug In With Battery Backup Electrochemical Sensor Carbon Monoxide Alarm With Test ButtonElectrochemical Sensors Are The Most Accurate Technology Available For Detecting Carbon MonoxideSingle Button Test/Silence For SimplicityLoud 85dB Alarm To Assure Alarm Is HeardEnd Of Life Alarm Notifies You At 84 Months After InstallationPower Source: 120V Outlet With 9V Battery Backup (Included)