Energizer, 9V, Advanced Lithium Battery, Recommended For Use In Home Improvement & Professional Audio Devices. Can Be Used Up To 10 Years As A Back Up Battery In AC Powered Smoke Detectors. Up To 2 Times Longer Storage Life, Works In All Temperatures, -40 Degrees To 140 Degrees Fahrenheit, Lightweight, 25% Lighter Than Alkaline 9V.