Middle-capitalization stocks and exchange traded funds have attracted greater interest over the years with their better risk-adjusted returns. However, investors may not want to overweight the asset category as valuations are looking pricey.

There are a number of broad mid-cap stock ETF plays that investors have looked over. For instance, the iShares Core S&P Mid-Cap ETF (NYSEArca: IJH) and SPDR S&P MidCap 400 ETF (NYSEArca: MDY) both track the S&P MidCap 400 Index, with about 69% mid-cap exposure and 31% in small-caps. [The Lengthy Out-Performance of Mid-Cap ETFs]

The Vanguard Mid-Cap ETF (NYSEArca: VO) provides an alternative as it follows the CRSP US Mid Cap Index, but the it also includes a 20.2% weight in large-caps, along with 79.0% mid-caps.

Investors can also consider the Schwab US Mid-Cap ETF (NYSEArca: SCHM), which follows the Dow Jones U.S. Mid-Cap Total Stock Market Index. The index holds 86.8% mid-caps and 10.4% small-caps.

Alternatively, there are a number of smart-beta index ETFs that tilt toward mid-cap stocks due to their indexing methodologies. For example, the Guggenheim S&P 500 Equal Weight ETF (NYSEArca: RSP) equally weights S&P 500 stock components and includes 46.7% mid-caps, 40.2% large-caps and 12.8% mega-caps.

“With higher returns than large caps but less risk than small caps, mid-caps have generated better risk-adjusted returns,” writes Morningstar analyst Michael Rawson. “But with elevated valuations, now may not be the best time to overweight mid-caps.”

Showing Page 1 of 2