As sports fans enjoy the legacy-defining moments of this month’s N.B.A. finals and Stanley Cup finals, Jason Arasheben is studying like a college student before exams.

Arasheben, a celebrity jeweler whose clients include the rappers Drake and ASAP Rocky, is investigating the history of the contending teams, the connections to their cities and any other interesting facts that could be infused into an extravagantly bejeweled ring. He is also scouring his personal contacts for anyone who could facilitate a meeting with the wealthy owners of the winning franchises.

“You just have to start connecting the dots,” said Arasheben, the chief executive of the Jason of Beverly Hills jewelry house near Los Angeles. “Billionaires talk to other billionaires.”

In the past few years, Arasheben has established himself as a go-to jeweler for title-winning teams — carving out a corner of the market long dominated by Jostens — by creating dynamic rings that include reversible faces and detachable compartments.

“He’s reimagined what the championship ring is all about,” said Eric Tosi, the chief marketing officer of the Vegas Golden Knights, who won the Stanley Cup last year.

“Every team that wins a title no matter the sport is going to get a ring,” Tosi continued. “But how can you stand out? How can you do something that’s never been done before? He’s done that.”

Arasheben uses both word of mouth and cold outreach to gain new clients, and his reputation has grown rapidly. In the past five years, he has designed championship rings for nine professional teams, including the reigning N.B.A., M.L.B. and N.H.L. champions.

ARASHEBEN, WHO BEGAN making and selling jewelry at the University of California, Los Angeles, created his first professional sports rings when the Los Angeles Lakers won back-to-back N.B.A. titles with Kobe Bryant in 2009 and 2010. A close acquaintance, he said, introduced him to Jesse Buss, a son of Jerry Buss, who owned the Lakers at the time.

Jason of Beverly Hills now has more than 100 employees and competes against jewelers such as Tiffany & Company and Baron. But at the time, it was a budding company with about six employees and sparse infrastructure.

Arasheben said that he and his team occasionally slept in the factory in sleeping bags and that in 2009, it finished the last ring about 30 minutes before the unveiling ceremony. (He has also designed four rings for the Golden State Warriors, the Lakers’ 2020 ring, the Denver Nuggets’ 2023 ring and the 2022 ring for the W.N.B.A.’s Las Vegas Aces.)

Just before the Bucks won the N.B.A. finals in 2021, a mutual friend connected Arasheben to Alex Lasry, whose father, Marc, was formerly part of the franchise’s ownership group. But that relationship alone did not seal the deal.

The team’s president, Peter Feigin, said Arasheben’s hands-on approach convinced the team to select him over three other options. “What separated him is he took ownership at the C.E.O. level of wanting to do it,” Feigin said.

Along with team executives, Bucks players Giannis Antetokounmpo and Khris Middleton helped in the creative process. Antetokounmpo’s brother Kostas had won the N.B.A. finals with the Lakers the previous season, and Feigin said Giannis wanted a larger ring than his sibling’s.

Arasheben suggested making a removable top that could transform into a pendant.

“Athletes are naturally competitive, but owners are also competitive,” he said. “They want to outdo each previous ring, so the rings are getting bigger every year. I’m not sure how much larger they can get, otherwise they’ll be plates.”

THE MORNING AFTER the Los Angeles Rams won the Super Bowl in 2022, Tony Pastoors, the team’s vice president of football and business administration, had an email from Arasheben waiting in his inbox.

“‘I’m from L.A. Your team is from L.A. It only makes sense,’” Arasheben said, recalling his pitch. “I probably was draining Tony’s batteries with how many times I called and emailed him.”

Pastoors was already familiar with Arasheben, who had designed the Super Bowl ring for the Tampa Bay Buccaneers the year before, and had the star Rams players Jalen Ramsey and Odell Beckham Jr. as personal clients.

The Rams owner, E. Stanley Kroenke, and his son, Josh, were particularly interested because they wanted a local jeweler, Pastoors said. When Arasheben and Pastoors met for a meal, he brought the Buccaneers ring and the most recent Lakers ring, stunning everyone including the restaurant servers.

“It was a very ‘wow’ moment,” Pastoors said. “As always with Jason, he found a way to bring some flash.”

Pastoors said some players collaborated with Arasheben while he solicited feedback from executives. Arasheben also called Pastoors to ask for some of the artificial turf and footballs used during the Super Bowl.

“He was like, ‘Why on earth do you need a ball?” said Arasheben, who integrated slivers of those materials into the ring.

STANLEY CUP RINGS have been predominantly silver toned. But the Vegas Golden Knights wanted a gold ring to correspond with their name, said Tosi, the chief marketing officer.

“We thought that would be a differentiator, ” Tosi said. “Being in Vegas, the expectations are high for the quality of the look and the storytelling behind it.”

Yellow diamonds are tougher to source than white ones, Arasheben said, and the shades must match throughout the ring to avoid a slipshod aesthetic. He traveled to Canada, Belgium and Israel searching for diamonds, he said.

“I didn’t tell them how difficult that was going to be because that’s not their problem — it’s my job to figure it out,” Arasheben said of his first hockey championship ring.

Arasheben would not disclose how much his rings cost teams, but they might order hundreds to accommodate players, owners, coaches, executives and staff members.

On the Golden Knights’ ring, the team’s helmet-and-shield logo is embossed above yellow stones. But about three weeks before the unveiling ceremony, Arasheben added white diamonds to the logo for contrast and even more bling.

“That put it over the top,” Tosi said.

THE OWNERSHIP OF the Texas Rangers preferred a conservative ring without special features after winning the World Series last year, said Travis Dillon, the senior vice president of marketing.

Even so, the team’s art director recommended Arasheben after hourslong research of his rings in other sports, Dillon said. It would be the first World Series ring for both the Rangers and Arasheben.

“I walked into the meeting already having a really trusted resource,” Dillon said. “They had a strong endorsement out of the gate internally.”

Throughout the design process, Arasheben presented digital copies and wax molds of modest-style rings. But in the final meeting with executives, he revealed a detachable top.

Everyone loved it, Dillon said, because the mechanism served a purpose and allowed more statistics to be inscribed into the base. Arasheben said he was nervous about the potential reactions to his surprise. But he needed to try.

“That’s what is expected of us,” Arasheben said. “That’s the reason we broke into this industry.”