Tretorn's pressurized balls are the world's first 3-piece multi layer tennis balls with a unique TRI-TEC™ sealing membrane. This membrane helps to maintain the ball's pressure and performance significantly longer than conventional pressurized balls which over time lose bounce and playability due to loss of air pressure.

Along with this revolutionary pressure retention technology, Tretorn's pressurized balls feature exclusive Milliken felt and a rubber core designed for playability and consistency, making these the ultimate tour performance balls.

Serie+ has been the Official Ball of the worldwide ATP Challenger Tour since 2007. The ATP Challenger Tour is of great importance to the health of professional tennis worldwide and provides fans with an opportunity to catch a first glimpse at the stars of the future.