iShares National Muni Bond ETF seeks to track the investment results of the ICE AMT-FreeUS National Municipal Index. The fund will invest at least 80% of its assets in the component securities of the underlying index and it will invest at least 90% of its assets in fixed income securities of the types included in the underlying index that BFA believes will help the fund track the underlying index. The underlying index includes municipal bonds, the interest of which is exempt from Federal income taxes and not subject to alternative minimum tax.