8" Type B Gas Vent High Wind Rain Cap 8GVVTH This high-wind rain cap is used for vertical terminations only. Provides improved performance in high wind conditions. For vertical terminations only. For Category 1 gas appliances 1" clearance to combustibles Easy-fit twist-lock design with no fitting hassles 0.012" aluminum inner 0.018" galvanized outer .010†Double-wall aluminum flex inner wall (two-ply .005â€) .018†galvalume outer wall with twist-lock connections.