Specifications include, but are not limited to: Penn Coach Practice Balls Pro Penn Marathon Extra Duty Tennis Ball Wilson Revolve Spin Tennis StringFeaturing innovative pentagonal shape construction and low-friction UHMW material for generating incredible biteand snap-back. Wilson Revolve Twist Tennis StringNewest evolution of Revolve franchise places emphasis on enhanced spin and control, innovative 3-bump twistconstruction includes sharp edges to grab the ball, generating incredible bite and snap-back, ideal for big hittersand aggressive players. as powerful shots can be roped into play with the added spin and control. Babolat Pro Hurricane Tennis String Reel Extremely durable, great combination between spin and control due to the co-polyester composition and theoctagonal structure