In the last trading session, U.S. stocks managed to hold on to modest gains in what was overall a rocky session thanks to higher oil prices and downbeat employment data. Among the top ETFs, investors saw SPY gain 0.37%, DIA go up 0.51% and QQQ surge 0.53% 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: SCHM: Volume 3.43 times average This mid-cap ETF was in focus on Friday as more than 777,000 shares moved hands. This compares to an average trading day of 226,000 shares and came as SCHM gained nearly 0.4% on the session. The big move was largely the result of a weaker-than-expected reading on the U.S. labor market that can have a big impact on mid-cap stocks like the ones we find in this ETF portfolio. Mid-cap investing provides a safer option with the potential to move higher in an unstable market. SCHM was up nearly 2.2% in the past one month and currently has a Zacks ETF Rank #3 (Hold). BIL: Volume 2.83 times average This 1-3 month T-bill ETF came in under the microscope on Friday as roughly 4.3 million shares moved hands compared to an average of roughly 1.5 million shares. We also saw marginal stock price movement as shares of BIL advanced 0.02%. A slide in 3-month treasury yields following a flight to safety favored the T-bills. In the last one month, BIL was up about 0.04%.The fund has a Zacks ETF Rank #3. 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 >>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 SCHWAB-US MC (SCHM): ETF Research Reports SPDR-BC 1-3M T (BIL): ETF Research Reports SPDR-SP 500 TR (SPY): ETF Research Reports NASDAQ-100 SHRS (QQQ): ETF Research Reports SPDR-DJ IND AVG (DIA): 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