Gamma Pro is a 17-gauge / 1.2 mm squash string:

There’s a new string out from Gamma called the Gamma TNT² squash string. Gamma also have a set of tennis strings with the “TNT squared” name, but these yellow ones are specifically made for squash. There are two thicknesses, the 1.1mm and the 1.2mm. Gamma TNT² 1.1 The thinner version. I tested this one out…