Conformable fiberglass casting tape

An orthopaedic casting tape containing a fibrous substrate impregnated with a water-reactive polyurethane prepolymer, said substrate comprising a combination of a high modulus fiber and an elastomeric fiber which is not substantially reactive with the prepolymer and which will maintain its elastic properties for at least 12 months after impregnation with the prepolymer, the elastomeric fiber being incorporated in the substrate in the length direction of the substrate to give the substrate an extensibility of between 40% and 200% in the length direction, said substrate having a power such that the force necessary to extend the substrate to 30% elongation is between 40 and 175 grams per inch of substrate width.