... Flange, TDC Flange, Air Duct Flange Duct Flange For HVAC Ducting System Octopus Metal Co., Ltd is the leading HVAC Ductwork ... 1.5 million M2). We operates 4 efficient production sites for galvanized rectangular air duct manufacture. Our duct works are certified ... by China National Accreditation Service for Conformity Assessment (CNAS). Octopus Metal offers wide range of ...