Assuming I didn't want to trade VIX futures, which ETF makes the best substitution? I am interested in the ETFs because: 1) no rollovers 2) OEC doesn't offer VIX futures I've seen the following: VXX (S&P500 short-term futures) IVO (inverse) XXV (inverse S&P500) 2x: SVXY (ProShares short VIX short-term) TVIX (VelocityShares Daily 2x VIX short-term) VZZ (Long Enhanced S&P500 mid-term) VXZ (S&P500 VIX mid-term futures) VIXM (ProShares mid-term futures) VIXY (ProShares short-term futures) XVIX (daily long-short VIX) What is the difference between short, mid, and long term with regard to VIX indexes? I understand the difference between the regular and the 2x ones. Some of them are not what I expect. For example, here is a chart comparing VXX with XXV, which I would expect to be exact opposites of each other, yet they are obviously not: Even two VIX ETFs that have the same description, such as TVIX and VIXY (both are 2x short term) are not even: What's going on? Why is there so much difference between products with identical descriptions?