MANTIS T-POWER is a 17ga (1.25mm) solid core synthetic gut string. It features a compressed core that results in excellent tension maintenance, superb control and impressive power. While MANTIS markets this product as a squash string we have been using it for tennis it is every bit as good, if not better than many 17ga synthetic gut tennis strings. Th compressed core allows it to blend nicely with poly-basd mains and it does well at lower tensions and holds up well. This string rocks and is an absolute steal as we clear it out for $19.90.