12" DuraVent DuraChimney II Chase Top Flashing 12DCA-CTF This chase top flashing encloses the top of a chase while providing a ventilation air passage to the chase. Includes spacer clips. Approved for wood coal oil and Category 1 gas 430-alloy inner wall 021" galvanized outer Double-wall air cooled chimney system 2" clearance to combustibles Factory-built alternative to pre-fabricated masonry chimneys Lightweight design which eliminates the need for field assembly of pipe sections allowing for faster installation Tested and listed for continuous operation at 1000 ° F flue gas temperatures one hour at 1400 ° F and ten-minutes at 1700 ° F .016†430 stainless steel inner wall and .021†galvanized steel outer wall. For stainless steel outer wall