Majorly tennis balls are classified as pressurized and pressureless balls.
Pressurized – All balls are pressurized to some extent. As the bounce is a key factor, such balls have a hollow core, filled with nitrogen. With The help of a tennis ball pressurizer tube you can easily increase or maintain the pressure in the tube.
In general, tennis ball pressurizer tube this used to ensures that new tennis balls will never lose their bounce.
Tennis players can enjoy playing with proper pressurized tennis balls, without needing to replace or put up with balls that go soft. Instead the balls keep bouncing like new balls until the felt completely wears out! It is by far the most economical choice for tennis enthusiasts.
If you do not use the pressurizer than these balls generally loses their pressure after about a month or so after opening the pressurized can that they come in. As they lose their pressure, they become “dead” and do not bounce so well. Some tennis ball manufacturers use nitrogen in the center, because this air tends to last longer.
Pressure less – This type of pressure less tennis balls has a solid core and is suitable for those training themselves in the game. The ball does not lose its bounce easily. A practice ball may have less pressure, but they are more durable to last longer. As they age, they will lose fuzz from the surface. The performance will then vary as the ball loses its aerodynamic properties.
These balls have a solid core and their core is made out of synthetic threads or any other small material that helps maintain their durability and consistency. Their core tends to last longer, therefore bouncing is not affected even though they bounce less than pressurized balls, and as far as the external felt.
Both the kind of balls have their own pros and cons it depends on you which balls you want to use. Browse this link to read out detailed pros and cons of pressurized and pressureless balls