First Alert PR700LB Smoke Alarm, 9V Lithium,5-13/64" Low Profile Slim Design - Sleek, contemporary design blends into any decor. Photoelectric Smoke Sensor - Reduces false alarms commonly caused by cooking smoke and shower steam. Silence Feature - Silence unwanted alarms. Test alarm with the same button. Tamper Resistant Locking Pin - Locks alarm to to base to prevent removal of battery. Perfect for apartment, dormitory or hotel applications. 9V Lithium Battery Included.