The investment seeks to replicate as closely as possible, before fees and expenses, the price and yield performance of the MVIS® U.S. Listed Oil Services 25 Index. The fund normally invests at least 80% of its total assets in securities that comprise the fund's benchmark index. The index includes common stocks and depositary receipts of U.S. exchange-listed companies in the oil services segment. Such companies may include small- and medium-capitalization companies and foreign companies that are listed on a U.S. exchange. The fund is non-diversified.