Product Description Wilson Sporting goods Duo control 4gr 125 & NXT c 16 Tennis String, Natural Wilsons Duo control is a hybrid string that blends NXT control with Luxilon 4g Rough for a string bed that scores well in spin, precision and tension maintenance For ideal playability, reduce tension on Luxilon 4g Rough at least 10% Either string can be installed in the mains for superior control and performance California Prop 65 Warning : This product can expose you to chemicals including arsenic, which is known to the State of California to cause cancer. For more information visit to the website.