Treasury bond

US government debt with maturities of 20 or 30 years. Highest duration in the Treasury market — most rate-sensitive instrument outside zero-coupon bonds. TLT (20+ year Treasury ETF) lost ~50% from late-2020 peak to late-2023 trough as long rates rose from 1.5% to 5%.

Used by pension funds for long-duration liability matching. Hedge funds use them for macro bets on the long end of the curve.