Signum Pro Firestorm is a high-tech co-poly with a crisp and comfortably firm response. It also has above average power for a poly-based string. Strung at the low end of the tension range, this one has impressive levels of comfort, touch and pop. Strung tighter, it still retains its excellent feel but also offers impressive control. The spin-potential is excellent. While it is best suited to advanced players with sound mechanics and big strokes, this co-poly is user-friendly and powerful enough to work for strong intermediates looking to make the leap into a control string.