Municipal bond exposure should be a core consideration by investors who want to construct a balanced portfolio. Historically, the market has been dominated by retail investors allocating into single assets without much focus on risk characteristics, but over time the broader exposure offered by mutual funds has grown in popularity. However, the newest and most significant growth sector has been passive ETF funds. This paper explains the risk characteristics of this new growth sector and highlights FTSE Russell's new set of muni bond indices and their performance relative to corporates and treasuries.