Flexible duct: Diameter range: 4 20 (102 508mm) Temperature range:-30 140 The highest air flowing speed: 30m/s The largest work pressure: 2500pa. Glass Fibre thickness:25mm Glass Fibre density:20kg/m3 Standard length:10m/7.62m Flexible thermally insulated duct are made of standard flexible duct. Apply for low/medium/high pressure air rentilation and air conditioner systems. At high temperatures or in case of fire, no toxic gas emission. Easy to install oval or round connection!