Duracell Ultra with M3 technology is the most powerful Duracell Alkaline battery ever made, especially for high-drain devices. The secret is in the revolutionary M3 technology which is packed with even more active ingredients and reformulated to improve electron flow. This works to make your devices run longer and work better. That’s what makes it last up to 50% longer than ordinary alkaline batteries. All Duracell Ultra Alkaline batteries come with PowerCheck, Duracell’s patented battery tester, which lets you know when it’s time to buy more batteries.