For Rafael Nadal, it's a lifelong association with Babolat, for Roger Federer, it's a Wilson while world number one Novak Djokovic is powered by Head.
Tennis amateurs may dream of emulating the stars by using the same racquets as their idols, but the 'Big Three' of the sport are very specific when it comes to their needs.
Suppliers, too, keep the tricks of the trade close to their chests.
"The racquet is vital for the career of any player, it's an extension of the arm," Nadal, about to embark on his bid to win a 21st Grand Slam, told AFP.
"It is through it that sensations pass and at the end of the day, without a good feeling with your racquet, it's very difficult to get success.
"If I try another racquet today I won't be comfortable at first. Whereas with my racquet I feel good because I know it inside out, I know where to hit, I know what I can do.
"At all times, I know how the ball can react to the movement I am making."
Nadal has been firing forehands and backhands all over the world with a Babolat racquet in his hand.
His relationship started when he was just nine when he and his Uncle Toni, his coach for the majority of his greatest triumphs, walked into a sports shop in his home town of Manacor.
With his 35th birthday just around the corner, he has never changed his equipment supplier.
It's a partnership for "his entire career and even beyond", said Babolat chief executive Eric Babolat who is as starstruck as many as the Spaniard's fans.
When they saw Nadal play, the company's top brass said to themselves "a UFO has arrived, what can we do?," he said.
At Roland Garros in 2020, when Nadal captured his 13th French Open title, he was using his personally-branded racquet.
Developed over the years in close collaboration with Nadal, the result was a carbon composite frame weighing 300 grams without the strings, which anyone can buy.
But from there, the made-in-China frames go through the lab at Corbas, near Lyon, where they are then tailored to suit Nadal.
To customise a racquet, it takes 20 to 90 minutes of work for an additional cost estimated between 150 and 200 euros.
First, there is a personalisation of the handle -- size can be refined, shape adapted even to the point of carving a slot for a finger.
Technical customisation will follow -- the addition of material on the frame or in the handle to modify the racquet for power or its centre of gravity for precision.
"It's tailor-made, we work on different sizes, different playing intentions, to adapt the racquet to the player's needs," said Sylvain Trinquigneaux, engineer at Babolat's performance laboratory.
The settings remain confidential.
"Involving all our players in research and development would be ideal, but it's impossible," added Trinquigneaux.
"However, Rafa is Rafa. His feedback is super interesting and super enriching. Ditto for Dominic Thiem."
However, for those players, professional or amateur, looking for a factory-made magic wand, Trinquigneaux has bad news.
"The ideal racquet does not exist."