Duct fittings and combinations, such as ells, tees, and reducers, are responsible for balancing airflow and equalising duct pressure. It's an air distribution box for an HVAC system's central distribution and collecting air flow unit.
Sheet metal ducts, fibreglass lined ducts, and fiberboard ducts are the three basic forms of rigid ducting.
Duct fittings are the components that are used to connect the ducts in a space so that they can ventilate it. The standard size for these fittings is 4 inches.