Set of 2 The First Alert SM210 10-Year Sealed Battery Smoke Alarm with Slim Profile Design is available in a convenient two pack. The SM210 smoke alarm features First Alert's Precision Detection advance sensing technology and meets new industry standards. This slim profile alarm is easy to install, and the 10-year sealed battery means no battery replacements are required. Precision Detection technology helps reduce cooking nuisance alarms and provides early warning. 10-Year sealed battery eliminates battery replacements and low battery chirps for the life of the alarm Slim profile design is half the depth of a standard alarm End-of-life warning lets you know when it?s time to replace the alarm Test/silence button for efficient testing to ensure alarm is working properly