7" DuraVent DuraTech Aluminum Storm Collar 7DT-SC This storm collar is required with DuraTech flashing to create a weather-proof penetration through the roof deck. Seal inner edge of the collar to the chimney pipe with non-hardening 500 ° F high-temperature sealant. 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.