First Trust Vest U.S. Equity Buffer - May 

First Trust Cboe Vest U.S. Equity Buffer ETF ? May seeks to provide the holders of Units (?Unitholders?) with returns (before fees, expenses and taxes and, in respect of the units only, any changes to the Canadian/U.S. dollar exchange rate) that match the price return of the SPDR® S&P 500® ETF Trust (the ?Underlying ETF?) up to a predetermined upside cap (before fees, expenses and taxes and, in respect of the units only, any changes to the Canadian/U.S. dollar exchange rate), while providing a buffer against the first 10% (before fees, expenses and taxes and, in respect of the units only, any changes to the Canadian/U.S. dollar exchange rate) of a decrease in the market price of the Underlying ETF, over a period referred to as the ?Target Outcome Period?.