Highly popular MUB offers a broad and representative basket of muni bonds in an efficient package. The funds portfolio aligns reasonably well with our benchmark, with a bias toward general obligation bonds. Most of the security issuers are state and local governments or agencies such that interest received is exempt from US federal taxes. The index considers bonds of investment-grade rating only but with final maturity of greater than or equal to one month. The bonds are market-value weighted in the portfolio and rebalanced after the close on the last business day of each month. Prior to March 1, 2016, the fund name was iShares National AMT-Free Muni Bond ETF, and prior to September 15, 2021, the underlying index for MUB was the S&P National AMT-Free Municipal Bond Index.