EMERGENCY STROBE™ is powered by one "D" cell alkaline battery (not included) which will allow it to flash at 60 to 70 times per minute for up to 16 continuous hours and then at a diminished flash rate for up to a total of 60 hours. This personal protection light is visible for up to 3 miles, depending on atmospheric conditions. It easily attaches to a backpack, belt or Personal Flotation Device by its stainless steel locking pin. It is U.S.C.G. and S.O.L.A.S. approved as a PFD/Safety light, and is an ideal accessory product for all outdoor activities. "Making others aware of your location" , can be a very valuable lifesaving benefit in a variety of situations, on land or on the water. The magnetic "reed" on/off switch, waterproof case and hard amber acrylic lens cover make this a very unique safety product. $17.95Lens Color: 5013-A Amber5013-R Red5013-B Blue5013-C Clear Colored Replacement Dome LensInterchangeable dome lenses will make your strobe light useable for multiple purposes. LENS-$2.00Color: A AmberC ClearB BlueR Red D-Cell Alkaline Battery AL-D$0.85 Need more information? Please feel free to contact us at 1-800-592-6940 - Ask for Extension 547 or Internet Sales.