Residential HVAC Installation Practice Exam

This is because a transition fitting is specifically designed to connect different sizes of square or rectangular ducts together. An elbow fitting is typically used to change the direction of the duct, while a reducer fitting is used to change the size of round ducts. A connector fitting is used to join two ducts together, but it does not change the size of the duct. Therefore, as none of the other options are designed to change the size of a square or rectangular duct, the correct answer is a transition fitting.