5" & 7" DuraVent DuraTech Adjustable Galvalume Wall Strap 5DT-AWS This adjustable wall strap stabilizes chimney while ensuring a minimum 2" clearance to combustibles. Can adjust out to 6" clearance if needed. 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.