It is usually a slow-burning material, similar to black powder that has had various compounds added to it to produce visible smoke, usually black, white, or yellow in color. This section exists so that the rocket will be seen when it reaches its maximum altitude, or apogee. The ejection charge is finely powdered black powder. It burns very rapidly, exploding, in effect. The explosion of the ejection charge pushes out the parachute of the model rocket.
Rocket engines have their own peculiar labeling system.
The letter is an indicator of the power of an engine. The number following the letter is the approximate thrust of the engine, in pounds. The mixture is bound together by an epoxy.