Money managers including BlackRock and CSOP Asset Management have registered a total of nearly 40 exchange-traded funds (ETFs) tracking mainland shares and debt with US regulators, Bloomberg reported, citing regulatory filings. The products allow anyone with a US brokerage account to gain exposure to Chinese securities that were previously off limits to all but a few qualified institutions, and come as equities in China head for their biggest annual gain since 2009. With the Hong-Kong Shanghai bourse linkup set to open mainland stocks to greater outside investment, fund providers are rushing to stake claims to the fees they hope will come from new investors.