batteries aligned in the housing in a manner to provide a compact unit while electrical components may be mounted to circuit boards positioned transversely to the length of the flashlight application_number US 6170305 A description with initial reference to fig2 a flashlight 10 includes a main generally cylindrical housing 12 defining an interior space or cavity in which illumination source 14 ballast 16 drive electronics board 18 and batteries 20 are located the housing 12 is preferably constructed of an appropriate durable metal such as an anodized aluminum alloy which allows it to serve as a circuit element while providing both corrosion resistance and heat dissipation the front end of the housing carries lens 22 which is held to the front of the housing by retaining ring 26 which is affixed to the front of the housing by bolts 28 a gasket assembly 24 seals the lens from water entry the housing may be preferably milled out of a solid piece of stock with a forward cavity portion 30 for the bulb ballast and drive electronics board three parallel cavity portions 32 each dimensioned to receive a stack of batteries 20 and a rear open ended cavity portion 34 which accepts the rear cap 36 each of the battery cavity portions 32 connects with forward cavity portion 30.