Duracell CopperTop alkaline-manganese dioxide battery with flat terminals. Get dependable, long-lasting power from CopperTop batteries with Duralock Power Preserve technology. These batteries have been engineered to deliver just the right level of power for most of your household needs. Plus, they now have up to a 10-year guarantee in storage. Many of the devices use in home are powered most efficiently by Duracell CopperTop batteries with Duralock, including toys, clocks and radios, remote controls, smoke alarms, flashlights, portable electronics, calculators, wireless mice and keyboards.