In just under three months of trading, FTSM has quickly become one of the most successful new ETFs to debut this year, amassing nearly $506 million in assets under management. Among new ETFs, that total is surpassed only by the First Trust Dorsey Wright Focus 5 ETF (NasdaqGM: FV), which debuted in early March. [Another Good Year for New ETFs]

The actively managed FTSM invests in short-duration, investment-grade securities with the objective of delivering current income while providing capital preservation.

Short-term bond ETFs are also gaining favor as alternatives to money markets as regulators implement new requirements on money market accounts. Specifically, the new rules require institutional prime money market funds to float their net asset value, which will allow the daily share price of the funds to fluctuate along with changes in the market-based value of fund assets, essentially breaking the so-called buck, or constant share price of $1.00, that many have come to expect.

ETF Trends editorial team contributed to this post.