The fund offers representative exposure to mortgage pass-through securities. It has exposure to the three major agencies: Fannie Mae, Freddie Mac, and Ginnie Mae. Instead of holding actual MBS pass-throughs, the fund uses MBS TBAs as liquid alternatives to the MBS. The fund uses a sampling method in tracking the index, which means it will invest in a sample of securities that collectively have an investment profile similar to that of the underlying index.