The iShares 20 Plus Year Treasury Bond ETF (TLT) tracks the prices of 20+ year duration bonds and generally moves inversely to the 20/30 year Treasury yield. Because it gains when yields fall, it is one of the few assets that are guaranteed to appreciate during a hardcore recession or crash which warrants emergency rate cuts by the Federal Reserve. The last two hike cycles allowed for a 25% - 40% appreciation (if timed perfectly).