In the last trading session, U.S. stocks saw rocky trading sparked by another round of selling in oil prices that has aggravated concerns over the global slowdown. Among the top ETFs, investors saw SPY losing 0.1%, DIA adding 0.4%, and QQQ move higher by 0.6% on the day.Two more specialized ETFs are worth noting as both saw trading volume that was far outside of normal. In fact, both these funds experienced volume levels that were more than double their average for the most recent trading session. This could make these ETFs the ones to watch out for in the days ahead to see if this trend of extra-interest continues:JKL: Volume 9.30 Times AverageThis small-cap value ETF was under the microscope as 66,000 shares moved hands. This compares with an average trading day of roughly 8,000 shares and came as JKL shed 0.2% in the trading session.The movement can largely be blamed on heightened volatility that led to higher appeal for value ETFs. Additionally, small caps are less vulnerable to international headwinds. JKL has shed 10% in a month’s time and carries a Zacks ETF Rank #3 (Hold) with a Medium risk outlook.IUSG: Volume 4.54 Times AverageThis growth ETF was in the spotlight as more than 3.9 million shares moved hands compared with an average of 922,000 shares a day. We also saw some price movement as IUSG gained 0.4% in the last session.The big move was largely the result of an expected rate hike by Fed that can have a big impact on growth stocks like what we find in this ETF portfolio. IUSG has lost 5.9% over the past month and carries a Zacks ETF Rank #2 (Buy) with a Medium risk outlook.Want key ETF info delivered straight to your inbox?Zacks’ free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week. Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report SPDR-DJ IND AVG (DIA): ETF Research Reports ISHARS-CR USG (IUSG): ETF Research Reports ISHARS-MO SC VL (JKL): ETF Research Reports SPDR-SP 500 TR (SPY): ETF Research Reports NASDAQ-100 SHRS (QQQ): ETF Research Reports INVS-STR US (IUS): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report