This unit comes with a trim ring to cover existing screw holes and fit newer units into previous installation cutouts. Compact size, designed for the rugged RV EnvironmentAdvanced Technology. Alarm Mute button silences alarm while RV is ventilated. Rapid recovery sensor resets when silenced or reactivates alarm if dangerous levels of CO remain.Memory Scan™ Retains the CO level that activated the alarm.12 Volt power means no missing or dead batteries to replaceLow Current Draw(37 mA). Innovative micro current circuit saves battery powerOperating Temperature: -40°F to +158°FApproved. Meets RVIA/NFPA requirements