The Fund is an actively-managed exchange-traded fund (ETF). The Fund pursues its objective by investing principally in a national portfolio of both municipal and taxable fixed-income securities. The Fund invests, under normal circumstances, at least 80% of its net assets, including any borrowings for investment purposes, in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax for certain taxpayers. The Fund may invest in fixed-income securities rated below investment grade (commonly known as junk bonds), although such securities are not expected to be the Funds primary focus. The Fund may invest in securities issued or guaranteed by Puerto Rico or its agencies or instrumentalities.