Power up your play with the HEAD Hawk 17 1.25mm 12m tennis racket string in Green. This string features Crystal Core technology for explosive performance, designed for power and control. HEAD Hawk tennis strings are built with Crystal Core technology, a multistage thermal treatment that creates distinct differences between inner and outer parts of the string. The result is increased elasticity and greatly improved energy efficiency, giving you easy access to unrivalled power. Gauge: 17 (1.25mm) Length: 40ft (12m) Composition: Copolyester monofilament. The Head Hawk tennis string has been developed in co-operation with Head's top pro players to deliver extraordinary energy efficiency. It provides more feel and power than a conventional polyester string and has a monofilament core for improved durability. The string is supplied as a 12m (40ft) set, which is enough to re-string one racket.