He doesn’t own a smartphone, he largely relies on mental math, and he only uses a computer to play bridge under the name “T-Bone.”

But even without the modern conveniences the rest of us take for granted, it doesn’t take long for Warren Buffett to decide whether looping a company into the Berkshire Hathaway family is worth it or not.

On Tuesday, the Oracle of Omaha sat down David Rubenstein, co-CEO of the Carlyle Group, on Bloomberg.

When asked by Rubenstein if he receives calls from people every day, hoping to pitch him the “perfect” deal, Buffett said his phone rings less than expected because Berkshire brk.a has a clear-cut criteria.

“When somebody calls, I can usually tell within two or three minutes whether a deal is likely to happen or not,” Buffett told Rubenstein. “There’s just half-a-dozen filters,” he said, gesturing toward his head. “And it either makes through the filters or not.”

 

One of these unsolicited pitches came from Eitan Wertheimer, chairman of Israeli metalworking company Iscar, back in October 2005. Wertheimer’s proposal came in the form of a letter, and although it was just one and a quarter pages long, it was enough to pique Buffett’s interest. Iscar’s management team visited Omaha a month later.

Buffett decided to buy 80% of Iscar for about $5 billion in May 2006. Berkshire later bought the rest of the company for $2 billion in 2013.

Berkshire Hathaway also decided on its largest acquisition with the same speed. The company agreed to buy Precision Castparts in a $37.2 billion in Aug. 2015.

Rubenstein asked Buffett if he had spent a year studying the company given the cost of the deal, and Buffett responded with “No.” Buffett said that he met Precision’s CEO, Mark Donegan, just a month before the deal was announced, heard him talk for 30 minutes, liked him, and decided that he was interested in offering a bid.