Its double-bearish exposure ProShares UltraShort 20+ Year Treasury ETF (NYSEArca:TBT) is the single biggest leveraged and inverse exchange-traded fund in the world. ProShares, the worldâs biggest purveyor of inverse and leveraged ETFs, filed paperwork with the Securities and Exchange Commission to market four exchange-traded funds that give investors tools to manage various inflationary scenarios over 10- and 30-year periods. It said such funds should be used only by knowledgeable investors who understand how daily rebalancing works and who actively monitor their investments.