As a result of several factors which may include changing interest rates, refundings, and sales or defaults on the underlying securities, there is no guarantee that distributions will either remain at current levels or increase over time. Estimated current return is determined by dividing a Trusts estimated net annual interest income per unit by the public offering price per unit. Estimated long-term return is a measure of the estimated return over the estimated life of a Trust. Unlike estimated current return, estimated long-term return reflects maturities, estimated principal prepayments, Trust charges and expenses, and discounts and premiums of securities in a Trust. Returns and prices will fluctuate. Consult a prospectus for a more complete description of the estimated net income, estimated current return and estimated long-term return calculations.