8" Type B Gas Vent Wall Strap 8GVWS This wall strap is used to provide support for offsets and horizontal runs. Recommended every 4' to support vertical common vent. Use also with DuraConnect or DuraConnect II. Wall Strap legs can be rotated 360 degrees to conceal screw. 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.