7" DuraVent DuraTech Galvalume Attic Insulation Shield 7DT-IS This attic insulation shield is required for installations that pass through an attic to prevent insulation and debris from accumulating near the chimney. Fits over firestop radiation shield or a support box. Consists of two parts: a collar and a base. 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.