The Tourna Restore Tennis Ball Repressurizing Tool keeps balls fresh. Restore maintains balls at their original pressure of 14psi, stopping natural leakage that occurs through rubber during storage in unpressurized cans. Restore will also re-pressurize balls for extended play. Twist down top seals and compresses air in. Extends the life of your tennis ball by storing them under pressure. Screw the halves together to create a pressurized environment equal to 14 psi, which is equal to an unopened can of balls.