Warren Buffett, the legendary investor known for his no-nonsense approach to putting his money into stocks and businesses, has some high praise for what is arguably the most-iconic of all Bay Area companies, Apple.

On Monday, Buffett, the chief executive of Berkshire Hathaway, called Apple “probably the best business I know in the world,” and said the iPhone maker is the third-largest holding in his Berkshire investment portfolio. In an interview on CNBC, Buffett said he “should have appreciated it earlier” and bought stock in Apple years before he began investing in the company.

“I don’t think of Apple as a stock,” Buffett said. “I think of it as our third business.”

Just how big of a business is Apple for Berkshire Hathaway?

In Buffett’s annual letter to Berkshire shareholders that he released on Saturday, Buffett said that at the end of 2019, Berkshire owned 5.7% of Apple’s outstanding shares, or 245 million shares of stock, worth almost $72 billion. The only larger holdings for Berkshire are its insurance businesses, which include Geico Auto Insurance, and its ownership of the BNSF railroad.

Buffett emphasized his enthusiasm for Apple by also saying he has finally ditched his $20 flip phone, and is now using an iPhone 11. Buffett said he made the move after being given several iPhones over the years, including some that came directly from Apple CEO Tim Cook.

But, Buffett was also quick to say that he remains pretty old-fashioned when it comes to his iPhone usage.

“I use it as a phone,” Buffett said. “You’re looking at an 89-year old guy who’s barely beginning to get with it.”