Model number SCO403; Bundles together a smoke alarm & carbon monoxide detector; Ionization smoke sensor reliably detects smoke from fast-flaming fires; Electrochemical sensor accurately detects carbon monoxide; Battery-operated alarms install easily without the aid of an electrician; Loud 85dB alarms; SA303 has 10-year limited warranty & CO400 has 5-year limited warranty; Includes 2 9V batteries & mounting bracket;