The investment seeks to track the investment results (before fees and expenses) of the S&P MidCap 400® Equal Weight Index (the underlying index). The fund generally will invest at least 90% of its total assets in the securities that comprise the underlying index. The underlying index consists of all of the components of the S&P MidCap 400® Index, a broad-based index of approximately 400 securities that measures the mid-cap segment of the U.S. equity market.