In the automotive world they were the mechanical device that engines, used to control the amount of gasoline going in to mix with the air. They worked well until about 1972 when emissions controls needed to be implemented. They were phased out by Fuel Injectors in the early 1980's. One of the last cars that used one was the 1985 Mustang 302 GT. Early fuel injectors were not that good, but today Fuel Injectors are FAR superior to any carberrater.