4" x 12", 4VP-WZAJ12, 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. Made from 304 stainless steel with a welded seam inner wall, combined with a galvalume, welded seam, outer wall for wood pellet, corn, oil fuel and biofuel burning appliances. Listed at 1" clearance to combustibles. Features fully unitized twist-lock construction in 3" and 4" diameters.