In the last trading session, U.S. stocks were in the green. The oil price recovery and the year-end optimism around Wall Street shrugged off Fed-induced worries. Among the top ETFs, investors saw SPY gain over 0.9%, DIA rise over 1% and QQQ move higher by about 0.7% on the day.

Two more specialized ETFs are worth noting in particular though as both saw trading volume that was far outside of normal. In fact, in the most recent trading session, both these funds experienced volume levels that were more than double their average. This could make these ETFs ones to watch out for in the days ahead to see if this trend of extra interest continues:

PXF: Volume 3.34 times average

This developed markets ex-U.S. ETF was in focus on Tuesday as roughly 517,661 shares moved hands compared to an average of roughly 154,850 shares. We also saw some stock price movement as PXF added about 0.7%.

The movement can largely be credited to the rise in oil prices and overall buoyant sentiment over global stocks after a few days of slump. In the last one-month period, PXF was down 4.5%. The fund carries a Zacks ETF Rank #3 (Hold).

SLYV: Volume 3.12 times average

This small-cap U.S. value ETF was under the microscope yesterday as nearly 74,437 shares moved hands. This compares to an average trading volume of 23,830 shares.We also saw some great stock price movement as SLYV gained about 1.6%.

While small-cap stocks can explain the U.S. economic growth well at present, the value tilt in it will be able to weather market upheaval caused by global growth worries and Fed-related shocks. In the last one-month period, SLYV was down about 8.3%. The fund has a Zacks ETF Rank #3.