There's a $129 million ETF that offers a unique safety net for investors hoping to avoid the next stock market crash. Here's how it works.

"40% of the entire market cap is made up of the 40 or 50 best companies in the United States," Lamensdorf, manager of the $129 million AdvisorShares Ranger Equity Bear exchange-traded fund (HDGE), told Business Insider by phone. Read more: We asked 6 chief equity strategists to break down the hottest trends in the stock market right now — and where you should be putting your money Lamensdorf's services come at a price: The expense ratio on HDGE is about 2.7%, much higher than many of the low-cost ETFs that are exploding in popularity. we don't have anything except we're short an equity security." Also, Lamensdorf says that timing the market — or just knowing when to beef up hedges — is a daunting task. To mitigate against this kind of reactionary emotional behavior, Lamensdorf publishes a Market Timing Report that combines various sentiment gauges, including the Ned Davis short-term indicator, to help this cohort of investors monitor the risk of losses on a six to nine-month basis.