16" DuraVent DuraTech Double-Wall Vertical Chimney Cap 16DT-VC1 16" DuraVent DuraTech Double-Wall Vertical Chimney Cap is required where pipe terminates above the roof line. Removable screws allow for cleaning of the chimney and spark arrestor screen. Made of stainless steel. Diameter: 16" Double-Wall Vent Construction Spark arrestor screen included Stainless steel construction Secure twist-lock connection 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.