AmeriVent pipe and fittings are lightweight and feature rugged, double-wall construction of corrosion-resistant galvanized steel and aluminum. Ends have a snap-lock coupling. Model E is available in sizes 3" through 6" diameters and has a ¼" airspace between pipe walls. Model R is available in sizes 7" through 30" diameters and has a ½" airspace between pipe walls. When calculating the assembled length, allow 1" length reduction for the overlap at each joint.