8" DuraVent DuraTech Galvalume Wall Thimble 8DT-WT This wall thimble adjusts from a minimum of 5 1/2" to a maximum of 9 1/2" wall thickness and fits between standard wall studs. To accommodate thicker walls the telescoping pieces can be extended up to 16" with a field-fabricated extension installed. Interior trim ring painted black. Must be installed with DuraTech chimney pipe horizontally through the wall and extend 6" into the room beyond the interior wall. 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.