Type-B Gas Vent products are tested and listed to UL 441 for approved gas appliances and feature our innovative twist-lock connection and locking tab, eliminating the need for sheet metal screws. Metal-Fab Type B Gas Vent combines hemmed flues and casings that maximize product durability and reliability and minimize installation time. Designed for versatility, Metal-Fab Type-B Gas Vent products 3"-6" adapt to major competing brands and when installed establish a UL Listed connection.