5" & 7" DuraVent DuraTech Galvalume Adjustable Elbow Strap 5DT-AES This adjustable elbow strap is used to prevent excessive weight on the elbows by supporting the weight of the chimney. Required to be installed between two elbows in offset installations. Multiple elbow straps may be required for offset installations. Refer to installation instructions. 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.