Yonex Dynawire Tennis String uses a solid core construction for a crisp feel and durable response. The string also incorporates a unique metal film around it for a boost in power, and silicone coating to help the strings slide easily. Dynawire is a solid all around synthetic gut string with a comfortable response.Construction: Solid Core Synthetic Gut with Silicone and Metal Film wrapColors: White | Blue | Black | Red | YellowGauges: 16 G / 1.30 mm | 16 L / 1.25 mmLength: 40 ft / 12 m