A race quad-copter requires propellers to translate the stored energy of the battery into kinematic energy. The structure of propellers are comparable to the wings of an airplane, which provides uplift when moving forward and lifts the plane off the ground.
The propeller causes a similar effect with the difference that not the whole plane needs to move forward. Instead, the uplift is created through the rotation of the propeller similar to a helicopter.
Plastic, Fiberglass or Carbon
Propellers can consisto of different materials. Small and in general inexpensive propellers are made of conventional plastic (e.g. EPP propellers). Improve quality of propellers is achieved through addition of carbon fiber or fiberglass. Propeller materials mixed of carbon- and fiberglass exist too. The best quality comes with a propeller consisting of pure carbon fiber because they are very light and highly efficient. Because of its expensive material and manufacturing process it is more expensive compared to a traditional plastic propeller.