The fund normally invests at least 80% of its assets in debt securities rated below investment grade (also referred to as high yield debt securities or junk bonds). The advisor uses the ICE® BofA® BB-B US High Yield Constrained Index as a guide in structuring the fund and selecting its investments as it relates to credit quality distribution and risk characteristics. The fund normally invests primarily in securities rated BB or B by S&P, Ba or B by Moody's, comparably rated by at least one nationally recognized credit rating agency, or, if unrated, considered by FMR to be of comparable quality.