TRU PRO Firewire (formerly Tier One Sports): An innovative, triangular shaped, monofilament string, offers one of the best ball bites and spin potentials in the string industry. Exceptional tension stability and its crisp but arm-friendly playing experience makes this string the front runner for the competitive weekend warrior. KEY FEATURES: Provides Maximum Ball Bite and Tension Stability. RECOMMENDED PLAYING LEVEL: NTRP: 3.0-5.0, UTR: 2.5-9.5 (intermediate - advanced level). GAUGES: 16g (1.30mm). 17g (1.25mm), 18g (1.20mm). LENGTHS: Sets: 12.2mm/40ft, Reels: 200m/656ft, COLORS: Red, Black. An innovative, triangular shaped, monofilament string, offers one of the best ball bites and spin potentials in the string industry. Exceptional tension stability and its crisp but arm-friendly playing experience makes this string the front runner for the competitive weekend warrior.