Barclays Global Investors added three new mega-cap exchange-traded funds to its lineup Friday, with the debut of the iShares Russell Top 200 Index Fund (NYSEArca: IWL), iShares Russell Top 200 Growth Index Fund (NYSEArca: IWY) and the iShares Russell Top 200 Value Index Fund (NYSEArca: IWX).

The funds charge 0.20 percent in annual expenses.

The new ETFs follow BGI’s success with the iShares S&P 100 Index Fund (NYSEArca: OEF), which has been on the market for nearly a decade and is the largest mega-cap ETF, with $2.3 billion in assets under management.

Michael Latham, co-CEO of iShares BGI, said in a statement that the new ETFs are being launched as a result of high demand from investors for more mega-cap products. The Russell Top 200 indexes measure the performance of the largest 200 U.S.-listed companies.

The funds enter a marketplace crowded not just by OEF but by a variety of funds. Rydex and PowerShares offer competing “core” products: the Rydex Russell Top 50 (NYSEArca: XLG) and PowerShares Active MegaCap Fund (NYSEArca: PMA), respectively.

Vanguard offers a trio of ETFs that will compete head-to-head with the new iShares: the Vanguard Mega Cap 300 Index Fund (NYSEArca: MGC), Vanguard Mega Cap 300 Value Index ETF (NYSEArca: MGV), and the Vanguard Mega Cap 300 Growth Index ETF (NYSEArca: MGK).

Long-only asset managers and many financial advisers turn to mega-cap ETFs during times of market uncertainty. By holding the “biggest of the big,” these ETFs are seen as safe havens compared with smaller-capitalization companies.

In that sense, the timing of the launch is good. The S&P 500 was down 1.9 percent in the trailing five days by midmorning on Friday, marking its biggest one-week tumble in more than three months.