"Y-Connector" or "Y-Joint" that is commonly used in HVAC ductwork. A Y-Connector is a type of duct fitting that is shaped like a "Y" and has two equal-sized branches and one larger-sized branch. It is used to connect three sections of ductwork together, where the two equal-sized branches are inserted into one section of ductwork, and the larger-sized branch is used to connect to the other section of ductwork.

The purpose of a Y-Connector is to allow the airflow from one section of ductwork to split evenly between the two equal-sized branches, which can be directed to different areas, such as separate rooms or floors in a building. This component is particularly useful in duct systems where there is a need to distribute air to multiple areas using a single duct.