The most common problem that every tennis player is to go through is a flat ball. This flat ball is enough to destroy the whole match as it makes your game bad. For years there is a long lasting discussion among tennis recreational players if there is a way to keep your tennis balls fresh for a long time.
Now, the solution to this problem is Tennis Ball Saver or Tennis Ball Pressurizer which can actually help to increase the durability of the tennis ball. First of all one need to understand that why do tennis balls wear out after some time.
Generally, the tennis balls are pressurized to 12 psi (pounds per square inch) more than normal air pressure. Normal air pressure around us is 14.7 psi, therefore pressure inside tennis balls is 26.7 psi.
These balls are sold in pressure cans, where the pressure is the same as the pressure inside of tennis ball. Therefore when you open a can with new tennis balls you can hear the hissing sound as the air leaves the can. The pressureless tennis balls can thus be used for more time with this equipment.
As soon as you open the can and start using the tennis ball, it will slowly wear out and become flat. The reason is that pressure inside the ball is higher than a normal air pressure around you and it starts to balance. Tennis balls are made from rubber which let some pressure to leave from inside of the ball.
To keep the balls fresh there is a tool called Tennis Ball Saver (pressurizer). It is a can where you put your tennis balls usually 3 and cover it with a lid. After twisting the lid you increase the pressure inside the can.
Click this link for detailed info on the tools for tennis balls. Tennis Ball Saver will not remake your used tennis balls to a new one. But it can slow the process of flattening out. Therefore tennis balls kept in ball Saver should be worn out later than balls kept in a tennis bag.