Vanguard Mid-Cap Growth Index Fund Admiral Shares 

This low-cost index fund offers exposure to the stocks of mid-capitalization U.S. growth-oriented companies, which tend to grow more quickly than the broader group of medium-sized companies. The fund seeks to track a growth-style index of medium-sized companies, whose stocks tend to be more volatile than large-company stocks. This potential volatility is one of the fund’s key risks. Investors looking to add a passively managed, mid-cap growth allocation to an already diversified portfolio may wish to consider this option.