The iPath US Treasury Flattener ETN (FLAT) is structured to provide investors with returns that are inversely correlated to the performance of the Barclays US Treasury 2Y/10Y Yield Curve Index. This specific index is built upon a strategy involving hypothetical investments in U.S. Treasury note futures, aiming to generate profits from shifts in the U.S. Treasury yield curve, whether it's steepening or flattening. To be more precise, the index's value rises when the yield curve steepens and falls when it flattens. Consequently, FLAT is designed to increase in value when the U.S. Treasury yield curve flattens and to decrease when it steepens.