(Reuters) - BlackRock has launched three new exchange-traded funds (ETFs), including two that offer exposure to the largest U.S. stocks and one designed to avoid them, reflecting asset managers' efforts to provide more tailored investment options.

The sustainability of the rally in mega-cap stocks has been one of the biggest talking points among investors. While advocates tout their outsized gains, critics are worried about frothy valuations and concentration risk.

Offering various options will allow BlackRock to tap the demand for equities regardless of investor preferences.

"The beauty of these ETFs is that they can be used by investors looking for more targeted exposure to mega-caps or those looking to diversify their exposure to large companies," said Rachel Aguirre, BlackRock's U.S. Head of iShares Products.

The iShares Top 20 U.S. Stocks ETF will offer access to the 20 largest U.S. companies.

The iShares Nasdaq Top 30 Stocks ETF will let investors hold the 30 biggest non-financial stocks, including mega-cap tech. It has secured backing from the University of California's investing arm.

The third product, the iShares Nasdaq-100 ex Top 30 ETF, will invest beyond the behemoths in the hopes of capturing the growth of relatively smaller tech firms.

The launch comes days after BlackRock debuted two ETFs to tap into the booming artificial intelligence space, leaning into thematic ETFs even as such funds lose their appeal.

MEGA CAP RETURNS

The top 20 companies in the S&P 500 have contributed more than two-thirds of the index's returns over the past three years, BlackRock said.

Roundhill Magnificent Seven ETF, which targets the so-called 'Magnificent Seven' tech giants, is up 40% in 2024.

BlackRock holds a portfolio of over 1,400 ETFs under its iShares business with more than $4.2 trillion in assets under management, as of Sept. 30. ETF inflows have been key to its growth strategy in recent years.