4vp-wzaj12, 4" x 12", adjustable pellet stove pipe, type l vent, gives installer the ability to add from 2-1/2" length to a maximum of 10-1/2" when slid over another piece of type l pellet pipe, proven coupling joint connects in seconds to assure joint integrity, gasketed joint design, double wall design with 1/4" airspace, inner wall 304 stainless steel, outer wall paintable galvanized, rolled over male end eliminates sharp edges, 1" clearance to combustibles.