The fund generally will invest at least 90% of its assets in the component securities of the underlying index and may invest up to 10% of its assets in certain futures, options and swap contracts, cash and cash equivalents, as well as in securities not included in the underlying index, but which the advisor believes will help the fund track the index. The underlying index measures the performance of public obligations of the U.S. Treasury that have a remaining maturity greater than one year and less than or equal to thirty years.