Threads already has more than 98 million users less than a week after its launch.

Elon Musk continues to lash out at Mark Zuckerberg as Meta’s Twitter clone, Threads, closes in on 100 million users.

Since the new platform’s launch last week, Musk has been highly critical of Threads, Instagram’s newest companion app and a direct competitor to Twitter. In the past few days, the Tesla CEO and owner of the beleaguered social media site has gone after Threads’ features, and even filed a lawsuit accusing Meta of poaching ex-Twitter employees to create the “copycat” app.

But on Sunday, the attack was a simpler one.

“Zuck is a cuck,” Musk tweeted under a screenshot of a Threads exchange between Zuckerberg and the account for fast food joint Wendy’s, referencing a sexual fetish in which someone enjoys watching their partner fornicate with someone else.

He then abandoned all subtlety in tweeting a final request: “I propose a literal dick measuring contest. ”

It’s the latest attack from the billionaire, who has spent the past week critiquing Zuckerberg’s personal history and the concept behind Threads. Musk even at one point challenged his rival to a mixed martial arts match.

On Saturday, he called Threads “just Instagram minus pics, which makes no sense, given that thirst pics are the main reason people use that app.”

Zuckerberg has unleashed his fair share of jabs as well—albeit a bit more understated. He tweeted for the first time in 11 years on the day of Threads’ launch. It was a meme of two spidermen pointing at each other, drawing a clear parallel between Threads and Twitter.

He’s also replied to more than a few Threads posts mocking Musk—including the aforementioned Wendy’s post.

Despite the billionaire beef, there’s much for Zuckerberg to be boastful about. Threads already has more than 98 million users less than a week after its launch, according to data from Quiver Quantitative.

Musk’s Twitter is still in the lead, however, with an estimated 368 million Twitter users worldwide as of December 2022, per Statista.

Whether Musk and Zuckerberg’s strange, social media-fueled beef is just playful banter or bitter competition remains to be seen.

Both have signaled their openness to the MMA match Musk is angling for—at least according to UFC President Dana White, who claims to have spoken with both men and estimates the revenue that could be generated from the fight to be upwards of a billion dollars.

“100 percent [they want to fight],” White said earlier this week. “I do [have a date in mind], I’ll announce it when we’re ready. It won’t be UFC 300.”