HEAD Hawk Reel 660' - BlackHEAD Hawk Reel 660' Black When the perfect balance of control and explosive power comes together in a string, we call it HAWK. This monofilament string's inner crystalline core, which influences control, and the outer molecular chains, which influence power, are perfectly balanced thanks to the innovative Crystal Core Technology, a unique manufacturing process. Highly durable and with high spin potential, these strings are the perfect weapon for the