First Trust Vest U.S. Equity Buffer ETF - May seeks to provide the unitholders with returns (before fees, expenses and taxes) that match the price return of the SPDR® S&P 500® ETF Trust (the "Reference ETF") up to 16.08% cap (before fees, expenses and taxes), while providing a buffer against the first 10% (before fees, expenses and taxes) of a decrease in the market price of the Reference ETF, over a period of approximately one year from the Monday following the third Friday of May of each year to on or about the third Friday of May of the following year.