Head Sonic Pro Tennis String - 1 Reel - 17 gauge - White Designed to improve elasticity, Head Sonic Pro 17 provides additional spin than its thicker 16 gauge version and offers up a unique combination of polymer additives to give a strong, yet flexible string. This combination of properties allows the string to remain durable, while providing additional power and depth in comparison to the typical polyester-based strings... Size - (See Description) | Color - (See Description) Authorized Head Dealer. All racquets are strung and ready for the courts! SEE SELLER DETAILS FOR RETURN POLICY.