The Department of Justice is amending the regulations of the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) to clarify that the requirements of part 555 do not apply to model rocket motors consisting of ammonium perchlorate composite propellant, black powder, or other similar low explosives, containing no more than 62.5 grams of total propellant weight, and designed as single-use motors or as reload kits capable of reloading no more than 62.5 grams of propellant into a reusable motor casing. This final rule is intended to provide rocketry hobbyists with guidance to enable them to enjoy their hobby in compliance with the safety and security requirements of the law and regulations.