Vanguard S&P Mid-Cap 400 

The fund employs an indexing investment approach designed to track the performance of the S&P MidCap 400® Index. The index measures the performance of mid-size companies in the United States. The Advisor attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the index, holding each stock in approximately the same proportion as its weighting in the index.