Covers designation system, dimensions and gauging of four series of pipe screw threads in the range 4 to 150 mm (1/16 to 6 in) nominal size (bore), suitable for connecting pipes used for conveying fluids, with sealing being effected on the thread surfaces in contact. The series are internal taper (Series RC), internal parallel (Series RP), external taper (Series R) and external parallel (Series RL).