The ATN Extended Life Battery Kit will make sure your optics don't quit before you're ready to. This easy-to-carry kit provides up to 15 additional hours of power to your ATN binoculars or monoculars so you can keep scouting, bird watching or glassing without going dark. Use your devices longer and save money (and space) devoted to carrying extra batteries. You 'll also be helping the environment by keep more out of landfills, too. The lithium ion battery is rechargeable and can be used to power non-ATN devices that are compatible with a micro USB as well.