This newly designed heptagonal string is made in two steps. The Signum Pro is designed with a new heptagonal mold with which it is given a first shape; This is the first step. Once cooled, it is reheated and rotated around the central axis; this is the second step. The twist and the double heating make this string very comfortable and that the surface, being rough, generates good effects. The result of this new technique is a string that combines ball grip, power and comfort.