Air Box/Air Cleaner
An airbox is an empty chamber which is present on the inlet of most combustion engines. It functions by collecting air from outside and feeds it to the intake hoses of each cylinder. It slows the air down and converts the kinetic energy of the air into static pressure.
However, a good airbox is diffuser like shaped which is 'bent' round a corner,and you may easily determine by assuming incompressibility, so on that bases Bernoulli's equation is valid which tells us that the pressure increases because the air slows down.
Older engines used to draw air directly from the surroundings into each individual carburetor. Modern engines instead draw air into an airbox, which is connected by individual hoses to each carburetor or directly to the intake ports in fuel-injected engines, thus it avoids an extra intake manifold.
Howbeit, some airbox manufacturers are Qingdao Hua Yushun Commercial Co., Ltd, LCH Electronic Co.Ltd, KE MA Industrial Co.Ltd, etc.