Longer runtime 9V - Tenergy's 4 pack 9V Lithium batteries offer 2.5 times more power than traditional 9V batteries. Provides enough power to last up to 10-years as a backup battery in ac-powered smoke detectors. Low self-discharge - Tenergy 9volt lithium battery features ultra-low self-discharge of only 2% a year and are date stamped for freshness. These batteries will provide power, even after 10 years in proper storage. Rounded fit - Tenergy's non-rechargeable batteries 9 volts is slightly slimmer with rounded edges and corners ensuring a wider fit in 9volt electronics. Wide temperature range - Use these batteries in your devices outdoors or inside and receive reliable power whether it's as cold as -4°F or as hot as 140°F. Tested and certified by UL standards. Included with every purchase is free lifetime support from our local team based in California.