Tennis Balls Explained: Regular vs Extra Duty, Pressureless and When to Change

What is actually inside a tennis ball

A tennis ball is two hollow rubber half-shells glued together into a sphere, then covered with two dumbbell-shaped panels of felt bonded on with adhesive. The regulation ball is roughly 6.5 to 6.9 cm across and weighs about 56 to 59 grams, and it must rebound within a specified range when dropped from a set height onto concrete. That last test is the one that matters to you — it is the standard a ball fails as it ages.

The felt is not decoration. It is what creates the drag that keeps the ball in the court, what your strings grip in order to generate spin, and what determines how the ball skids or bites off the surface. A bald ball flies differently, spins less, and is genuinely harder to control.

Most balls you buy are what the ITF calls Type 2, the standard-speed ball. There are also faster and slower official types — a harder, lower-bouncing ball intended for slower surfaces like clay, and an oversized, slower ball for very fast surfaces — plus a separate high-altitude category. In practice, unless a tournament specifies otherwise, the yellow ball on the shop shelf is Type 2 and you never need to think about the rest.

Pressurised vs pressureless

Pressurised balls have air inside the core at higher pressure than the surrounding atmosphere, which is why a can hisses when you open it — the can is pressurised too, to stop the balls going flat on the shelf. The internal pressure is what gives a new ball that lively, springy feel and the sharp, clean sound off the strings.

The catch is that rubber is not perfectly airtight. Air escapes through the shell slowly all the time, and much faster once you start whacking the ball, because every impact flexes the wall and forces gas out through microscopic gaps. That is why a pressurised ball has a short, definite lifespan whether or not the felt is intact.

Pressureless balls have no internal overpressure at all. Their bounce comes from a thicker, stiffer rubber wall instead. Because there is no air to lose, they hold their bounce for months or years — they will outlast their felt many times over. Some players even claim they get livelier as the felt wears down.

The trade-off is feel. Pressureless balls are heavier through the air, harder on the arm over long sessions, and lack the crisp response that makes a new can of pressurised balls so satisfying. Serious players almost universally prefer pressurised for real play. Pressureless are the right answer for ball machines, hopper drills, teaching baskets, backboard practice and anywhere a bucket of balls sits in a shed for a year between uses.

Regular duty vs extra duty: it is about the felt

This is the label people most often ignore and most often get wrong. The core is identical. The difference is entirely in the felt covering, and it exists because different court surfaces attack a ball in completely different ways.

Extra duty felt is thicker and tougher, and it is made for outdoor hard courts. An acrylic-over-asphalt court is essentially fine sandpaper, and it will strip a thin felt in no time. The extra thickness buys durability. The cost is that an extra duty ball plays a fraction heavier and slower.

Regular duty felt is thinner with a tighter nap, and it is made for clay, grass and indoor courts. On clay, the priority is keeping the surface material out of the felt. A tight, thin nap resists picking up clay; a thick, open one drinks it in. Regular duty also plays a touch lighter and quicker, which suits softer surfaces.

• Outdoor hard court — extra duty. Regular duty felt will start pilling and separating within a session or two and go bald fast.
• Clay — regular duty. Extra duty balls pick up clay, fluff up, get heavy and turn the game into a slog.
• Indoor hard or carpet — regular duty. The surface is far less abrasive, and the thinner felt is kinder to it.
• Grass — regular duty, and expect green stains regardless.

High-altitude balls

If you play somewhere meaningfully above sea level — roughly 1,200 metres or 4,000 feet and up — normal balls behave badly. Thinner air means less drag, so the ball flies further and faster, and the pressure difference across the ball's wall is larger, so it bounces higher. Rallies turn into a game of chasing balls that keep sailing long.

High-altitude balls are a recognised official category built to fix exactly that. They are pressurised at a lower internal pressure, so the effective difference against the thinner outside air is closer to normal, and they bounce noticeably lower on the standard drop test. On court, that translates back to something resembling a sea-level bounce.

If you live at altitude, buy them. If you are visiting Denver, Mexico City, Johannesburg or a mountain resort for a week, ask what the local courts use — clubs in those places usually stock them as standard, and turning up with sea-level balls is a quick way to spend an afternoon hitting the back fence.

How fast balls die, how to tell, and why matches use fresh ones

Faster than most people think. For a typical club player, a can of pressurised balls plays properly for something like two or three hitting sessions before the bounce is noticeably softer. Big hitters kill them much faster — a hard-hitting singles match can flatten a can in an afternoon, and competitive players routinely notice a drop within a couple of hours of play.

Two tests settle any argument. First, the drop test: hold a used ball and a brand-new one at shoulder height and let both go together. If the used one comes back visibly lower, it is finished. Second, the squeeze test: a fresh ball resists; a dead one gives easily and feels spongy.

The on-court symptoms are just as reliable once you know them. Dead balls fly long, because they lose less energy off your strings than they should. They sit up rather than kick, so your topspin stops biting. Rallies feel heavy and slow, your slice does nothing, and your serve loses its sting. If both players suddenly seem to be hitting the ball worse, check the balls before you check your technique.

This is also why competitive tennis uses fresh balls on a schedule. On tour, new balls arrive after the first seven games — the extra two account for the warm-up — and then every nine games after that. It is not luxury, it is consistency: a match played on progressively deader balls is a match where the conditions change under both players. For your club league, opening a fresh can for a real match is cheap and makes an obvious difference.

Practice-ball economics

Once you accept that pressurised balls die quickly, the sensible approach is to keep two separate stocks and stop feeling guilty about it.

Match balls: a fresh can, opened on the day. That is what a real match deserves and it is not an expensive habit.

Practice balls: everything the match balls become afterwards. A ball that is too dead for a league match is perfectly good for feeding drills, warm-ups, serve baskets and hitting against a wall. Most regular players end up with a permanent bag of yesterday's balls, and that bag is the cheapest coaching aid in tennis.

Buying in bulk is where the real saving lives. Cases of practice balls sold by the dozen cans cost far less per ball than singles from a pro shop, and if you serve a lot, a hopper of pressureless balls is a one-time purchase that lasts years. Ball machines should always be fed pressureless — feeding a machine fresh pressurised balls is money set on fire.

One caveat worth knowing: the cheapest supermarket balls are usually a false economy. Thin felt, low-quality rubber and inconsistent bounce mean they die faster than they save, and they teach you nothing useful about how a proper ball behaves.

Storing balls, and whether pressurisers actually work

Sealed cans are the best storage there is, but they are not permanent. Air escapes slowly even through a sealed can, which is why a can that has been in the cupboard for several years is measurably softer than one bought last week. Buy what you will use over a season rather than stockpiling.

Keep cans somewhere with a stable, moderate temperature. The boot of a car in summer or a freezing garage in winter both work against you — extreme heat accelerates the ageing of the rubber and adhesive, and extreme cold temporarily kills the bounce so you cannot even judge what you have. Refrigerating balls does not preserve them; it just makes them play dead until they warm up again.

Ball pressurisers are sealed tubes that hold used balls at roughly the same internal pressure as a factory can. The physics is straightforward: if the outside pressure matches the inside pressure, air stops leaking out, and balls that have already gone slightly soft can absorb some pressure back over a few days. They genuinely do extend the useful life of pressurised balls, and if you get through a lot of them, one will pay for itself.

What they cannot do is fix felt. A hard-court ball usually loses its felt before it loses its bounce, and no amount of pressure restores a bald surface. So a pressuriser is excellent for keeping practice balls usable much longer, and not a way to produce match-quality balls out of old ones. Manage your expectations and it is a good buy; expect miracles and you will be disappointed.

Red, orange and green: the kids' balls, and why they matter

Walk into any junior programme and you will see balls that are red, orange or green-dotted rather than plain yellow. These are not a gimmick or a cheap substitute. They are graded by compression, and they are the single best thing that has happened to junior tennis coaching.

The problem they solve is simple geometry. A standard yellow ball bounces to roughly chest or head height on an eight-year-old, and it arrives fast. A child faced with that has two options: swing wildly at a ball above their shoulders, or back up and let it drop. Neither builds a stroke. Reduced-compression balls travel slower and bounce lower, which puts the ball at waist height and gives the child time to step in and swing properly — the same conditions an adult gets with a normal ball.

The stages progress in step with court size and racquet length, so the game scales with the player rather than the player having to cope with an adult game.

• Red — the slowest and lowest, around a quarter of the compression of a yellow ball, often foam or oversized felt. Used on a short court with small racquets, typically ages four to eight.
• Orange — faster and bouncier than red but still well short of yellow, on a three-quarter-length court, typically ages seven to ten.
• Green dot — roughly 75% of a standard ball's compression, played on the full court. The last step before yellow, typically ages nine to eleven.
• Yellow — the standard ball, once a player has the strength, swing and court coverage to handle it.

The environmental angle, and what to do with old balls

Tennis has an awkward waste problem. Something in the region of 300 million balls are made each year worldwide, and only a small fraction are recycled or reused. In the US alone, estimates put well over 100 million balls into landfill annually — thousands of tonnes of rubber that takes centuries to break down.

The reason recycling is hard is the construction. A ball is rubber bonded to nylon felt with a strong adhesive, and separating those three materials at scale is genuinely difficult and expensive. It is not that nobody wants to; it is that a ball is a small, well-glued composite object.

That is changing, slowly. Dedicated non-profits now collect used balls in bulk, grind them, and turn the rubber crumb into court surfacing, equestrian footing and other products, and several major tournaments now route their used balls through those programmes rather than into a skip. Governing bodies also run schemes that redistribute playable used balls to schools, community programmes, care homes and animal shelters.

What you can do personally is unglamorous but effective. Do not bin them — keep a collection box in your bag and drop them at a club that participates in a collection scheme. Get more life out of each ball by using them for practice after they are done for matches, and by using a pressuriser if you hit a lot. Buy pressureless balls for your ball machine and hopper drills, where you would otherwise burn through cans. And give the genuinely finished ones away: schools, dog owners, walking-frame feet and craft projects all take them happily. A ball you hand on is a ball nobody has to manufacture.