While the institutional shares charge an expense ratio of just 0.08%, the ETF shares charge 0.13%. Vanguard notes that a 2006 Lipper study recorded an average expense ratio for large-cap ETFs of 0.17%.

The three funds track the MSCI U.S. Large-Cap 300 Index and its growth and value subindexes. Vanguard has other funds tracking the various size and style segments of the MSCI U.S. Broad Market Index, including ones tracking the MSCI U.S. Prime Market 750 Index, which combines MSCI's large- and mid-cap segments. With this latest launch, however, investors now have access to funds representing the three major nonoverlapping size segments.   

Although the original filing included investor shares, a Vanguard spokesperson said the firm believes the new funds will appeal mainly to institutional investors and financial advisors who prefer the flexibility of discrete small-, mid- and large-cap funds when constructing portfolios.

"We believe Vanguard's existing large-cap offerings provide most individual investors with sufficient, low-cost exposure to large-cap stocks, and therefore we chose to offer Institutional and ETF shares only," the spokesperson said, noting that individual investors could invest in the ETF shares. The ETF shares are cheaper than the investor shares would have been if they had been launched—their anticipated expense ratio was 0.20%.

You can view the prospectus for the new funds here.