Assumed Characteristics of the Mortgage Loans Underlying the Trust Assets¹: Principal Balance² Weighted Average Remaining Term to Maturity (in months) Weighted Average Loan Age (in months) Weighted Average Mortgage Rate³ Group 1 Trust Assets $225,000,000 352 7 6.50% Group 2 Trust Assets $183,200,000 320 38 6.50% Group 3 Trust Assets $295,911,000 357 2 6.44% Group 4 Trust Assets $462,900,000 350 9 6.50% Group 5 Trust Assets $129,569,000 246 103 6.50% ¹As of June 1, 2007. ²Does not include the Group 3 Trust Assets that will be added to pay the Trustee Fee. ³The Mortgage Loans underlying the Group 3 Trust Assets may bear interest at rates ranging from 0.25% to 1.50% per annum above the related Certifi- cate Rate. The actual remaining terms to maturity, loan ages and, in the case of the Group 3 Trust Assets, Mortgage Rates of many of the Mortgage Loans will differ from the weighted averages shown above, perhaps significantly. See "The Trust Assets – The Mortgage Loans" in this Supplement. Issuance of Securities: The Securities, other than the Residual Securities, will initially be issued in book-entry form through the book-entry system of the U.S. Federal Reserve Banks (the "Fedwire  Book-Entry  System").  The  Residual  Securities  will  be  issued  in  fully  registered, certificated form. See "Description of the Securities – Form of Securities" in this Supplement. Modification  and  Exchange:  If  you  own  exchangeable  Securities  you  will  be  able,  upon notice and payment of an exchange fee, to exchange them for a proportionate interest in the related Securities shown on Schedule I to this Supplement. See "Description of the Securi- ties – Modification and Exchange" in this Supplement. Increased Minimum Denomination Classes: Each Class that constitutes a Principal Only, Interest  Only  or  Inverse  Floating  Rate  Class.  See  "Description  of  the  Securities – Form  of Securities" in this Supplement. Interest Rates: The Interest Rates for the Fixed Rate Classes are shown on the front cover of this Supplement or on Schedule I to this Supplement. B-4