BUY IN BULK AND SAVE: Great value in this 660' reel of Black Widow polyester tennis string, PREMIUM POLYESTER TENNIS STRING: Premium polyester for unmatched power and control, EXCEPTIONAL SPIN: Heptagonal profile bites into the ball to give exceptional spin generation, ULTIMATE IN DURABILITY: High tensile, mono-filament premium polyester for extra durability, ADDITIONAL PRODUCT DETAILS: GAUGE: 16/1. 33mm. LENGTH: 660ft/200m.