... ventilation tube: Air duct,Air ducting, Ventilation duct. Air pipe,Ventilating duct. Ventilation equipment, Product: Square ventilation tube--Galvanized iron Our company, Qingdao Haiying Marine Equipment Co., Ltd ... . Our products - All kinds of ventilation fan,and ventilating duct, FAN---JCL( ... Certificate ISO9001:2000 with complete manufacturing equipment, advanced technologies and perfect testing ...