This specification covers nonvulcanized (uncured) rubber sheet made of ethylene-propylene-diene terpolymer (EPDM) or polychloroprene (CR) intended for use as watertight roof flashing exposed to the weather. In-place roof system design criteria such as fire resistance, field seaming strength, material compatibility, and uplift resistance, among others, are beyond the scope of this specification. The flashing material shall be formulated from the appropriate polymer type and other compounding ingredients, and shall be capable of being bonded to itself, to the roofing membrane, and to substrate for making watertight field splices and repairs. Property requirements for flashing before vulcanization include thickness, Green strength modulus, ultimate elongation, shelf stability, vulcanizability, tensile strength and set, dimensional stability, and weatherability. Consequently, the property requirements for flashing after vulcanization includes tensile strength and set, elongation, tear resistance, brittle point, ozone resistance, air oven heat aging, water absorption and weight change, linear dimension change, and weatherability.