In fact, the ProShares UltraShort 20+ Year Treasury ETF (NYSEArca:TBT) is the single-biggest inverse and leveraged ETF in the world. For example, a slew of inverse bond ETFs are becoming available that weren't around the last time financial markets headed into a cycle of rising rates, and it's important for investors to at least be aware of the choices that are out there. A combination of a strong equity markets and the near-certainty of inflation will force the Fed to begin raising interest rates in the coming months.