PHI Pre-Insulated Aluminium Ducts General standard: Size: 2000/4000*1200(L*W) CompressiveStrength:450kpa Thickness:20mm(also provide 25mm and 30mm) Water Absorption:2.90% Alum.Foil Thickness:0.08mm(both sides) Dimensional Stability:0.53%(70+/-2 Density:71kg/m3 Oxygen Index: 57.80% Fire Retardant: A Smoke Density: 2 Thermal Conductivity: 0.018W/m.k Smoke Toxicity: 25 (Average Temperature 25+/-2) Advantage : Lower heat conductivity, higher thermal efficiency; High Fire-Protection rating Low density, light weight; Easy Installation Foamed with CFC free materials, environment protective; Hermetic seal ensures little air leakage; With aluminum foil reinforced on both side, its corrosion protective, hygiene, and has a beautiful appearance; Foamed with closed-cell structure, its water-proof and sound-insulated. No protrudent flange on the connections, it can save a lot of building space. 1*40HQ.