In the manufacture of cordage (25), at least two groups (28, 29) of individually insulated, flexible conductors (21--21) which comprise a planar array (40) are moved through a core tube (71) of an extruder (27) in adjacent paths. As the groups are moved out of an exit portion of the core tube where they are spaced apart a predetermined distance and along converging paths to a die, a first plastic material is flowed about the array to enclose it and to be formed into a jacket by the die. Portions of the first plastic material flow between the groups to achieve an equilibration of pressure in the plastic material about each group, which controls the direction and magnitude of lateral movement of each group within the plane of the array, and to form a web (41) which is integral with the jacket and which may vary in thickness along its length to compensate for changes in the outside diameter of the insulated conductors. The control of the lateral movement of each group between the core tube and the die and the formation of a web results in a jacket having substantial symmetry and in cordage having the groups separated by the web which has a thickness that is substantially less than the predetermined distance. The jacket is coated with a second plastic material which has a stiffness modulus that is substantially greater than that of the first plastic material.