UCO seeks double the return of its futures-based index on a daily basisreflecting both the returns due to price changes on WTI futures contracts as well as any return (positive or negative) from rolling those futures contracts. As a geared product, UCO is designed for a one-day holding period, it`s not appropriate for buy-and-hold investors. Daily compounding can lead to the fund`s returns varying significantly from those of the index over holding periods of greater than one day. UCO is a great choice for a leveraged energy play.