Also known as the classic Ball Saver; the Gamma Revive Tennis Ball Pressurizer helps maintain the pressure of tennis balls. The pressurizer works by compressing atmospheric pressure between two cylinders to maintain 14 p.s.i. internal pressure when sealed, the same pressure inside your tennis balls when they are new. If left inside the Revive Ball Pressurizer long enough, a used ball will actually regain its original out-of-the-can pressure level.