Case

• The case holds the parts of the flashlight and is typically made out of either aluminum or plastic. Aluminum is stronger than plastic but plastic can be molded into different shapes and colored.
  
  

Batteries

• Batteries are the flashlight's power source. Most flashlights use C or D batteries, but small flashlights can use AA's and large flashlights use lantern batteries.
  
  

Lamp

• The lamp is the light source for the flashlight and contains either an incandescent or an LED lightbulb. LED bulbs are more efficient, but they don't produce as strong a light as an incandescent bulb.
  
  

Reflector

• The reflector rests around the light bulb and reflects the rays of light from the lamp. It consists of a piece of plastic coated with aluminum.
  
  

Lens

• The lens is a thin, clear piece of plastic located on the front of the flashlight. Usually, it's flat but some lenses have reflective ridges on the bottom to help focus the light. The main purpose of the lens is to protect the lightbulb.
  
  

Contacts and Switch

• The contacts are thin strips of metal that make an electrical connection between the batteries, the lamp and the switch, allowing electricity to be conducted. Contacts are usually made out of copper or brass. The switch turns the flashlight on and off by activating or breaking the flow of electricity in the electrical circuit.