A penlight is a small, pen-sized flashlight, usually containing two AA batteries or AAA batteries. In some an incandescent light bulb has an integral lens that focuses the light, thus no reflector is built into the penlight. Others use incandescent bulbs mounted in reflectors, while LED lamps are becoming increasingly common. Low-cost units may be disposable with no provision for the user to replace batteries or bulbs, and are sometimes imprinted with advertising for promotional purposes.
A headlamp is a flashlight designed to be worn on the head. A headlamp usually consists of the light emitter at the front, with a battery pack also attached to the front or back. The battery pack may be attached to the back of the head or in a pocket to improve balance. Headlamps leave the user’s hands free, making them popular for recreational and occupational activities.
Sometimes a tactical light is mounted to a handgun or rifle.
Most flashlights are cylindrical in design, with the lamp assembly attached to one end. However, early designs came in a variety of shapes. Many resembled modern day lanterns, consisting largely of a box with a handle and the lamp attached to the front. Some others were made to have a similar appearance to candles. Hand-held lanterns using larger batteries give greater running time, and, with large reflectors, can produce more concentrated beams better adapted to long-distance use.
Although most flashlights are designed for user replacement of the batteries and the bulb as needed, fully-sealed disposable flashlights do exist such as various inexpensive keyring lights. When the batteries in a disposable flashlight are depleted or the bulb fails, the entire product usually is thrown away or recycled and a new one purchased to replace it.
Two-part diving light with lamp assembly at left and battery pack at right, joined by a short cable. Diving lamps must be watertight under pressure and are used for night diving and supplemental illumination where surface light cannot reach.