Here is a recommended product: http://dx.com/p/100215 Brand: FandyFire Model: STL-V2 Color: Black Emitter Brand/Type: Cree XM-L Emitter BIN: T6 Color BIN: White Total Emitters: 3 Battery Configurations: 2 x 18650 batteries (not included) Voltage Input: 3.2~8.4V Switch Type: Clicky/Clickie Switch Location: Tail-cap Modes: 5 Mode Memory: Yes Mode Arrangement: Hi > Mid > Lo > Slow Strobe > SOS Circuitry: Digitally Regulated 1000mA Current Output Brightness: 3000 lumens maximum brightness (manufacturer rated) Runtime: 90 minutes at High mode (manufacturer rated) Lens: Coated Glass Lens Reflector: Aluminum Smooth/SMO