This specification covers rubber rings used as seals for asbestos-cement pipe joints. Material under this specification consists of natural or synthetic rubber rings, or both, for use in applications requiring non-oil resistant rings, and synthetic rubber rings for use in applications requiring oil-resistant rings. The ring shall be manufactured from a properly vulcanized virgin rubber compound, that is, rubber containing no scrap, reclaim, or rubber substitutes, with dimensions that shall conform to the requirements specified. The ring must also possess a surface that is smooth and free of pitting, cracks, blisters, air marks, and other imperfections, and a body free of porosity and air pockets. Tests for tensile strength, elongation, stress at elongation, hardness, compression set, low-temperature flexibility, volume change, and appearance change shall be performed and shall conform to the requirements specified.