In yesterday's trading session, U.S. stocks managed to hold on to gains in what was overall a rocky session. Among the top ETFs, investors saw (SPY - Free Report) gaining 0.1%, (DIA - Free Report) adding 0.05% and (QQQ - Free Report) move 0.4% higher 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.

(FRI - Free Report): Volume 6.69 Times Average

This real estate ETF was under the microscope as 505,000 shares moved hands. This compares with an average trading day of roughly 72,000 shares and came as FRI shed 2.5% in the trading session.

The big move was largely the result of falling yields that can have a big impact on real estate stocks like what we find in this ETF portfolio. FRI has lost 10.5% over the past month and carries a Zacks ETF Rank #3 (Hold) with a Medium risk outlook.

(SHV - Free Report): Volume 4.73 Times Average

This short-term Treasury ETF was in the spotlight as around 11.5 million shares moved hands compared with average 2.6 million shares a day. We also saw some price movement as SCHV gained 0.01% in the last session.

The movement can largely be blamed on concerns about global growth and interest rates that have raised the demand for short-term Treasury ETFs. SHV has added 0.2% in a month’s time and carries a Zacks ETF Rank #4 (Sell) with a Medium risk outlook.