They can be used for flue gas, ventilation ducts, etc.
Spark Arrestor Flue 60mm Stainless Steel, Tent Version
Chimney Anti-Wind Cowl Flue Liner Rain Cap Spark Arrestor Duct Pipe Cover
Chimney Anti-Wind Cowl Flue Liner Spark Arrestor Rain Cap Duct Pipe Cover
Chimney Anti-Wind Cowl Flue Liner Spark Arrestor Rain Duct Pipe Cover Protector
