14 CFR § 101.22

Class 1—Model Rocket means an amateur rocket that:

Uses no more than 125 grams (4.4 ounces) of propellant;

Uses a slow-burning propellant;

Is made of paper, wood, or breakable plastic;

Contains no substantial metal parts; and

Weighs no more than 1,500 grams (53 ounces), including the propellant.

Class 2—High-Power Rocket means an amateur rocket other than a model rocket that is propelled by a motor or motors having a combined total impulse of 40,960 Newton-seconds (9,208 pound-seconds) or less.

Class 3—Advanced High-Power Rocket means an amateur rocket other than a model rocket or high-power rocket.