The most common flashlight design is the simple household light that consists of a tube-like handle that contains the batteries. This handle is affixed to a threaded head assembly that houses the bulb mechanism. These units operate on standard batteries and provide a typical light output. Special designs are required for industrial or professional use. These lights are made from heavier gauge materials, and are more durable. They are also intended to produce a brighter beam of light. Flashlights with brighter beams are used by the police, firefighters, and the military.
These frequently use fluorescent tubes as their light source because of their greater energy efficiency, however, this type of bulb does not cast as strong or directed a beam of light. Furthermore, the increased size and weight of this type of lantern limits its portability.