flexible exhaust pipe material: Q195,Q215,Q235,Q345,20#,30#,45# etc ... steel pipes,welded Stainless Steel Pipe and so on .flexible exhaust pipe: 1) Material: Q195,Q215,Q235,Q345,20#,30#,45 ... : square steel pipe can be used in construction structure machinery, container rall structure, airport structure , shipbuilding and so on . 10) Packing ...