"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 15 lumen low mode. Its included rechargeable battery charges inside the light, using a standard USB cord. Dual-Fuel technology lets you swap out the rechargeable battery for primary (disposable) cells when needed"