First Trust Exchange-Traded Fund III - First Trust Ultra Short Duration Municipal ETF is an exchange traded fund launched and managed by First Trust Advisors L.P. The fund invests in fixed income markets of the United States. It invests in investment grade, tax exempt municipal debt securities issued by or on behalf of states, territories or possessions of the U.S. and the District of Columbia and their political subdivisions, agencies, authorities and other instrumentalities rated Baa3 by Moody's or BBB- by S&P or Fitch.