Kit Sizes: 1kg / 5kg / 21kg Grade 390 rubber is a high tear strength rubber for the casting of polyurethane resins. Its high tear strength permits castings to be made with larger than normal under cuts. When cured, it is stiffer that 370 and 380 giving it better dimensional stability. For casting in Clear PU plesae use Grade 400. Key Benefits: High Detail Pickup High Tear Strength Good dimensional stability Easy degassing Chemically resistant Pot Life: 45-120 minutes. De-mould: 8 hours Mixed viscosity: 19,500 mPa.s Cured Properties: Shore A hardness: 22° Elongation at break: 497% Tensile strength: 3.64 MPa Tear strength: 26.24 kN/m Young’s modulus: 1.5 MPa Linear shrinkage: 0.4% Min. service temperature: -50°C Max. service temperature: 200°C Pale blue (when mixed) Comes complete with hardener – mix-ratio is 5 parts of hardener to 100 parts of rubber.