Monday, China’s Shanghai Composite Index plunged greater than 5% for the second time in just two weeks, setting a one-month high in premarket trading for ProShares UltraShort FTSE/Xinhua China 25 (NYSEArca: FXP).

At 7:45 a.m. EDT, shares in FXP had traded up 45 cents at $11.05, representing a one-month high and topping the $11.04-level reached briefly on Aug. 17.

FXP aims to represent twice the inverse performance of the iShares FTSE/Xinhua China 25 Index (NYSEArca: FXI), an ETF that tracks the FTSE/Xinhua 25 Index. Shares in FXI were holding up well considering Monday’s giant sell-off, down just 1.06%.

Monday, the Shanghai Composite Index dropped 6.7%, over renewed concerns that a tightening money supply would put constraints on liquidity and equity purchases. The Index, which is China’s largest, ended the month 21.8% lower.

FXI’s largest three holdings, which constitute a quarter of the ETFs’ net asset value, all fell around an average of 4% in Asian trading. In Hong Kong, China Mobile dropped 2.9%, to HK$75.40, while China Life Insurance and China Construction Bank slipped about 5.5% each in Shanghai.

The gains in FXP may appear to be short-lived, however. After a big drop in mid-August, when the ETF climbed on Aug. 17 to its then one-month high, it dropped 2% the following day when Chinese shares rebounded suddenly. Market watchers in Asia expect declines in Chinese shares of around another 6% before a rebound comes in to play.

The continued decline is supported by options activity in FXP, where there is heavy buying of near-term $13 call options but a sharp drop-off thereafter.

ETFs that may be negatively affected  in the China sell-off include iShares MSCI Emerging Markets Index (NYSEArca: EEM), SPDR S&P China (NYSEArca: GXC), and PowerShares Golden Dragon Halter USX China (NYSEArca: PGJ), which has a relatively low diversification. WisdomTree Dreyfus Chinese Yuan Fund (NYSEArca: CYB), an ETF that tracks changes in the money market rates available to foreign buyers in China, may also dip lower.