3", 3RV-GC, Galvanized, Pipe Collar. Round Type B gas vent. This pipe collar provides a decorative and finished appearance for the pipe as it passes through the wall or ceiling of your living room. Form meets function as it also serves as a firestop. RV series offers round gas vent pipe and fittings for residential, commercial and industrial applications. It features a snap together, non-positional lock system, die formed ends and eliminates the need for all cutting, fitting and special engineering. 3", 3RV-GC, Galvanized, Pipe Collar. Round Type B gas vent. This pipe collar provides a decorative and finished appearance for the pipe as it passes through the wall or ceiling of your living room. Form meets function as it also serves as a firestop. RV series offers round gas vent pipe and fittings for residential, commercial and industrial applications. It features a snap together, non-positional lock system, die formed ends, and eliminates the need for all cutting, fitting and special engineering.