Description ITF Approved, Pressurized Balls Packed in a Pet can of 3 Balls. The Tretorn Series Tennis Balls feature extra durability on all court surfaces provided by a special mix of wool, cotton and synthetic fibres. Serie balls are the first tennis balls in the world with a unique TRI-TEC sealing membrane, which is used to retain air and keep balls pressure significantly longer than any conventional pressurised ball. Official Ball of ATP World Tour and ATP Challenger Tour.
