Metal-Fab 5M4ST Style "M" B-Vent 5"x5"x4" Tee. These light commercial and residential B-Vents feature a positive twist locking system designed for easy assembly and dis-assembly without bending or harming the product. The B-Vent Locking System comes standard on 3"- 6" pipes. The Metal-Fab 5M4ST Style "M" B-Vent 5"x5"x4" Tee is ideal for quick installation and long lasting performance. This Tee is ideal for connecting and reducing 3 lines with a single fitting.