This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.
The Aerotech RMS line of model rocket reload kits (of B through G power
levels) has been certified by the DOT for shipment as Class C Flammable
Solids. This means that the reload kits may be shipped the same as
other model rocket motors, such as those made by Estes and Quest.
There are no shipping restrictions of any kind on the motor casings and