The forward and rear bulkheads are threaded and screw onto the aluminum tube after the propellant is inserted into the casing. Various O-rings are used in the assembly to keep the burning propellant inside of the casing. Read the instructions and follow them carefully. Aerotech includes a small amount of grease with the casing assemblies. When the supplied grease has been used up you can use other greases such as bicycle chain lube or even KY jelly.
Composite motors get their name from the chemicals used to make up the propellant.
The binding rubber is also the fuel for the propellant. The chemical mixture of the composite motor is very similar to the propellant used in the Space Shuttle solid boosters. These prices are approximate and subject to wide variations.