Simpson Duravent 46DVA-48 4x7" Direct Vent Galvanized Pipe 48" DirectVent Pro is a complete venting system designed for use with gas direct vent stoves, heaters, and fireplaces. Safely vents flue gases, while providing incoming combustion air. Construction Materials: .020" aluminum inner wall with .018" galvanized steel outer wall. Dimensions: 4" ID x 6 5/8" OD x 48'' long.