"In keeping with ASP’s “two is one, one is none” philosophy of law enforcement lighting, the Guardian is a pocketable backup flashlight that packs the power of a full-sized duty light―well over 400 lumens, with a secondary (“Double Tap”) 15 lumen low mode. Its included rechargeable battery charges inside the light, using a standard micro USB cord, so there’s no need for a separate charging device. And if you don’t have time to recharge, or access to an outlet, ASP’s Dual-Fuel technology lets you swap out the rechargeable battery for disposable primary cells (AA and CR123A-compatible versions available). "