After Beijing opened the floods gates to foreigners, investors have been piling into Chinese A-shares. With everyone’s attention focused on mainland stocks, exchange traded funds that track Chinese company shares trading in Hong Kong are now looking cheap.

Over the past couple of months, investors have jumped into China A-shares, fueling a rally in mainland stocks. For instance, the Deutsche X-trackers Harvest CSI 300 China A-Shares ETF (NYSEArca: ASHR) surged 35.3% over the past three months. In contrast, ETFs that track China H-shares have been plodding along, with the iShares China Large-Cap ETF (NYSEArca: FXI) down 1.6% and SPDR S&P China ETF (NYSEArca: GXC) 3.4% lower over the past three months.

While the hot money chases the A-shares rally in Shanghai, identical company shares on the Hong Kong Stock Exchange are now about 16% cheaper than on the mainland, the widest gap since June 2012, Bloomberg reports.

For instance, China Petroleum, or Sinopec, traded at a 17% discount on the Hong Kong bourse, compared to Shanghai Thursday. China Petroleum makes up 3.3% of FXI and 2.0% of GXC.

Chinese stocks trading in Hong Kong were trading at a premium to stocks in Shanghai, but the roles reversed last month as China opened its market to more foreign investors by linking it with the Hong Kong exchange.

Additionally, the People’s Bank of China unexpectedly cut interest rates to support an flagging economy, which further fueled a surge in investment interest. [Something to Behold, A-Shares ETF Rally may Have More to Come]

Mainland shares “are dominated by retail investors, who don’t pay too much attention to fundamentals such as valuations,” Lu Wenjie, a strategist at UBS Group AG, said in the article. “Playing in a market with more inflow can make you money, so it’s natural that A shares are outperforming.”

The sudden interest in China A-shares is reflected in the growing premium in ASHR. U.S. investors’ thirst for A-shares ETFs has been so strong that on a couple occasions over Deutsche Asset & Wealth Management has been forced to announce limited creations for ASHR. Consequently, ASHR is now trading at a 6.0% premium to its net asset value, according to Morningstar data. [A Bumpy Ride for A-Shares ETFs]

“The premium could still widen near-term because of the strength of the bull run in A shares,” Jonathan Garner, head of Asia and emerging-market strategy at Morgan Stanley, said in the article.

iShares China Large-Cap ETF

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Max Chen contributed to this article.