170413 3"x18" Adjustable Length Pellet Vent BLACK 18 Pipe Adds 3-16 Of Length. Listed To UL 441. Marketed Exclusively To The Specialty Hearth Market. Laser-Welded (Not Spot Or Pop Welded) 304 Stainless Steel. Perfect Fit Construction Allows Ease Of Twist-Lock Connections While Eliminating Leaks - No Gaskets Or