Buy 4 or more for $8.25 per set. Crossfire ZX combines Ashaway's legendary Kevlar (once used by Andre Agassi) with a soft and slick Monogut ZX Pro. By combining a stiff and ultra spin friendly Kevlar main string with a lively and comfortable Zyex cross string, Ashaway delivers a phenomenal option to topspin players. This one offers truly massive spin potential. The low stiffness of the Monogut ZX Pro does a great job tempering the native firmness of the Kevlar main.