Billionaire investor Stanley Druckenmiller revealed a big bullish position in small-cap stocks last quarter, according to a new regulatory filing. The notable investor, who now runs Duquesne Family Office, bought call options against 3,157,900 shares of the iShares Russell 2000 ETF (IWM) for a stake worth $664 million. The bet marked Druckenmiller’s biggest one at the end of March. A call option gives an investor the right to buy an asset at a specified — or strike — price within a certain period. Investors profit from calls when the underlying securities rise in price. As of the end of March, Druckenmiller owned 31,579 call contracts with unknown value, strike price or expiry, according to the filing. Small caps have been underperforming their large-cap counterparts this year as cheap value shares lagged growth-oriented names. IWM is up nearly 4% in 2024, compared to the S & P 500’s 11% gain. Druckenmiller could be betting that the market leadership could rotate to smaller stocks as the rally broadens out. Money managers with more than $100 million in assets are required to disclose long positions with the U.S. Securities and Exchange Commission 45 days after a quarter ends. Theoretically, Druckenmiller could have already changed his positions by the time filings come out. The noted investor also took some profit in his big Nvidia bet last quarter by slashing the stake by more than 70%. Druckenmiller recently told CNBC that while he is still bullish on the artificial intelligence boom, he thinks the dramatic rally in the chipmaker made him pause. Indeed, the stock is up 90% in 2024. “We did cut that and a lot of other positions in late March. I just need a break. We’ve had a hell of a run. A lot of what we recognized has become recognized by the marketplace now,” Druckenmiller said on CNBC’s ” Squawk Box ” last week. Druckenmiller said he reduced the bet after “the stock went from $150 to $900.” “I’m not Warren Buffett — I don’t own things for 10 or 20 years. I wish I was Warren Buffett,” he added. Other than these changes, Druckenmiller added a sizable stake in semiconductor name Coherent , making it his eighth-biggest holding. Druckenmiller once managed George Soros’ Quantum Fund and shot to fame after helping make a $10 billion bet against the British pound in 1992. He later oversaw $12 billion as president of Duquesne Capital Management before closing his firm in 2010.