Gauge: 21 light (0.73mm). Color: Diamond blue with red and blue crosses. Advantages: 8-10% thinner string for greater power. 5000 Microfilament construction for optimum resiliency. Superior tension-holding at tournament level tensions. Usage: World class professionals and advanced amateurs. XL contruction for power players using high stringing tensions. String tension: Up to 33lbs (15kgs).