6" & 8" DuraVent DuraTech Galvalume Adjustable Extended Wall Support 6DT-XWS This adjustable extended wall support is used above the tee to provide support when bypassing obstructions or overhangs. Supports up to 20' of chimney. Tee support is not necessary when using this support. Approved for most fuel types 430-alloy stainless steel inner wall 2" clearance to combustibles ThermalTech blanket insulation eliminates hot spots Twist-lock connections for strong secure fits Able to vent large fireplaces and building heating appliances Clean smooth exterior finish 10â€-24†diameter pipes feature an .027†430 stainless steel inner wall and an outer wall of .029†galvalume or .027†430 stainless steel. A Refractory insulation is encased between walls. Only stainless pipes use the stainless end rings. Regular galvalume pipe uses galvalume end rings.