Not a shabby move.

The ProShares Short VIX Short-Term Futures ETF (SVXY) hit an 11-month high for shares outstanding last week and tallied its biggest inflows on record as volatility measured by the CBOE VIX Volatility Index (VIX.X) swung back down from an early-August rally.

The ETF typically gains when volatility falls and equity swings ease. Assets climbed to a record $1.3 billion, making the ETF the biggest of the most-used securities that bets on volatility, according to Bloomberg data.

The CBOE Volatility Index, also known as Wall Street's "fear gauge," slipped nearly 10% Monday to 12.90 following a rally earlier this month that saw the gauge climb as high as 16.9 points. 

The ETF gained nearly 4% by Monday's close and traded up about 1% pre-market Tuesday.

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