First Alert, 6 Pack, 120V AC Hardwired Smoke Alarm, With Battery Back Up, Equipped With An EZ Access Battery Door That Removes The Hassle & Burden Of Collecting Your Alarm From The Ceiling & Replacing Its Batteries, Provides Optimal Protection In The Event Of A Power Outage & An Increased Emphasis On The Unit’s 85 Db Output, Are Capable Of Interconnecting With Up To 18 Other First Alert Or BRK Hardwired Alarms, 10 Year Limited Warranty, Complies With UL217 Standards.