ProShares Advisors will launch its four “UltraShort” exchange-traded funds tomorrow on the American Stock Exchange. The new ETFs offer double inverse exposure to the Standard & Poor’s 500, Nasdaq-100, Dow Jones Industrial Average and S&P MidCap 400 indices. The funds come hot on the heels of eight ETFs ProShares – the ETF division of the ProFunds Group – offering leveraged (the “Ultra” funds) and short (the “Short” funds) on the same four indices. Those eight funds hit the market on June 21, and ProShares announced today that they have topped 1 million shares in trading volume.