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, which include a 68.7% tilt toward mid-caps and 31.2% to small-caps. [Interested in the U.S.? Look to ETFs that Target Smaller Companies.]

The Vanguard Mid-Cap ETF (NYSEArca: VO) provides an alternative as it follows the CRSP US Mid Cap Index, which leans towards larger companies with a 79.9% tilt toward mid-caps and 19.2% in large-caps.

Additionally, the Schwab US Mid-Cap ETF (NYSEArca: SCHM), which follows the Dow Jones U.S. Mid-Cap Total Stock Market Index, includes a 86.0% position in mid-caps and 11.1% in small-caps.

Investors can also look at small-cap ETFs, including the iShares Core S&P Small-Cap ETF (NYSEArca: IJR), Vanguard Small Cap ETF (NYSEArca: VB) and iShares Russell 2000 ETF (NYSEArca: IWM).

For more information on the S&P 500, visit our S&P 500 category.

Full disclosure: Tom Lydon’s clients own shares of IVV.

Max Chen contributed to this article.