Basketball superstar-turned-angel investor Shaquille O’Neal said he quadrupled his net worth using a simple investment strategy he learned from Amazon founder Jeff Bezos.

Shaq said he picked a strategy from Bezos of making “investments based on if it’s going to change people’s lives.” A four-time NBA champion and one of the game’s all-time greatest, Shaq said he attributes this to the growth in his net worth.

“Once I started doing that strategy, I think I probably quadrupled what I’m worth,” he said, adding that he only buys into something that his heart is into.

“If something comes across my desk and I don’t believe in it, I don’t even look at it,” he said.

Shaq racked up about $300 million from his two-decade career in the NBA and invested in “almost everything” including Google and Apple shares. He also has stakes in 24 Hour Fitness, a few nightclubs, 17 Auntie Anne’s, a Krispy Kreme franchise and a Big Chicken restaurant in Las Vegas.

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His net worth, according to a Forbes 2019 listing, is about $400 million.

At the age of 20, Shaq said he blew through $1 million in just one hour after signing his first professional basketball contract in 1992.

“My method is old school. Of course, there’s a lot of money to be thrown around but when you’re raised by a military drill sergeant, you have to do business honestly,” Shaq told Yahoo Finance in a recent interview.