PT Flex 20 Liquid Rubber is a two-part, liquid polyurethane system that cures (RTV) to a tan, Shore A23-25 rubber. This is the softest rubber in the PT Flex line of polyurethane mold rubbers. PT Flex Series rubbers were specifically designed for prototyping and model making applications and offer fast pour times (~4 minutes) and fast demold times (~2 hours).