Mergers and acquisitions are hot. Corporations flush with cash may not be hiring hordes of workers, but they aren’t just buying back shares or increasing dividends, either.

Global merger-and-acquisition volume totaled $2.4 trillion through late August, according to Dealogic. That’s a level not seen since the financial crisis.

Controversial tax inversions are a significant part of the recent deal flow, but to an even broader extent, big companies are looking down the market-cap scale and across the globe for growth engines. The U.S. has accounted for nearly half of the merger volume this year, driven mainly by technology and health-care deals.

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For investors—far from the Wall Street boardrooms and corporate law firms where these deals are hammered out—the problem is finding a way to tap into the merger boom. There isn’t a perfect way to play the trend, said Joe JJ Kinahan, chief strategist at TD Ameritrade. It’s hard to predict the next takeover target. And deals can be called off, sending a stock down 50 percent.

These ETFs are versions of a popular hedge fund strategy to bet on the stock prices of companies targeted in planned acquisitions once those deals are announced. Merger arbitrage ETFs diversify risk by spreading their bets across deals. The strategy is, in effect, a bet on the gap between the targeted company’s stock price after the merger announcement and its price when the deal closes.

A huge M&A market. for tiny ETFs

IQ Merger Arbitrage ETF. for example, is invested in some of the more high-profile and controversial deals currently in the M&A market. The ETF, which tracks the ETF company’s own M&A index, has roughly $62 million invested across roughly 45 global stocks, including the battle between Dollar General and Dollar Tree for Family Dollar Stores. Comcast’ s closely scrutinized bid for Time Warner Cable. Burger King ‘s deal with Tim Hortons —which has attracted attention related to the tax-inversion issue, and AT&T ‘s planned acquisition of DirecTV.

Returns are becoming more robust, said Adam Patti, CEO at IndexIQ Advisors. Cross-border deals are taking a greater piece of the overall merger pie. Larger companies want to play in many different markets.

IQ Merger Arbitrage has $62 million in assets and a 0.76 percent expense ratio, according to Morningstar.

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ProShares Merger ETF tracks the S&P Merger Arbitrage Index, but it’s small: $1.8 million in assets, according to Morningstar, spread among roughly 40 targeted companies. Its expense ratio is 0.75 percent.

Merger arb ETFs typically short equities in some manner while going long on the targeted stocks as a hedge. ProShares Merger ETF also shorts the stock of up to 40 acquiring companies; IQ Merger Arbitrage shorts global equities broadly. Both ETFs also invest in cross-border currency trades.