The Penn Championship Titanium tennis balls are an incredibly durable choice for demanding players that preserves the characteristics & fresh feel for longer due to increased core pressure retention within a natural rubber core. in addition, the balls additional longevity & enhanced visibility is ensured by a thicker grade of the felt. These USTA approved (United States Tennis Association) tennis balls guarantee a phenomenal feel as well as excellent playability through consistent specs & it is supplied as one dozen (12 tennis balls in total).