The Tecnifibre X-One tennis balls are both fast and durable to meet the needs of high level players. These top quality tennis balls are perfect for competitive use and incorporate the Grand Prix Formula rubber as well as a felt that is 72% natural. They are approved by ITF (International Tennis Federation) and FFT/ITF (French Tennis Federation/ Italian Tennis Federation). The balls are sold as a 12-dozen pack including 18 x 4-ball pressurised metal tubes.