The Municipal Bond ETF will seek to achieve its investment objective by investing primarily in a universe of investment grade municipal securities, the interest on which is exempt from regular federal income tax. Municipal securities in which the Portfolio may invest include, among others, revenue bonds, general obligation bonds, industrial development bonds, municipal lease obligations, commercial paper, variable rate demand obligations and other instruments (including participation interests in such securities) issued by or on behalf of the states, territories and possessions of the United States (including the District of Columbia) and their political subdivisions, agencies and instrumentalities. The interest on the municipal securities purchased by the Portfolio, in the opinion of bond counsel for the issuers and under current tax law, is exempt from federal income tax (i.e., excludable from gross income for individuals for federal income tax purposes but not necessarily exempt from state or local taxes). As a fundamental investment policy, under normal market conditions, the Portfolio will invest at least 80% of its net assets in municipal securities that pay interest exempt from federal income tax. The Portfolio does not currently intend to invest its assets in municipal securities whose interest is subject to the federal alternative minimum tax. Under normal circumstances, the Portfolio will generally maintain a dollar-weighted average duration of no more than one half year greater, and no less than one year below, the average duration of the Portfolios benchmark, the S&P Intermediate Term National AMT-Free Municipal Bond Index, which was approximately 3.70 years as of August 31, 2021. In making purchase decisions, if the expected term premium is greater for longer-term securities in the eligible maturity range, the Advisor will focus investment in the longer-term area, otherwise, the Portfolio will focus investment in the shorter-term area of the eligible maturity range. If a security has been redeemed by the issuer at a date prior to the stated final maturity date for the purposes of the above duration restriction, the early redemption date shall be considered the maturity date regardless of the stated final maturity. Duration is a measure of the sensitivity of a securitys price to changes in interest rates. The longer a securitys duration, the more sensitive it will be to changes in interest rates.