Duct Transition Fitting for 3-1/4 x 10 x 6 in Duct:Connects 3-1/4 x 10 in rectangular duct to 6 in round pipe. Made of thick galvanized steel for strong, leak-resistant, and rustproof performance. Smooth interior reduces airflow resistance. Easy to install, ideal for kitchen vents, dryers, and commercial HVAC systems.