Non-bank mortgage originator Resimac has launched a securitisation of prime residential mortgage-backed securities, to be known as RESIMAC Triomphe Trust - RESIMAC Premier Series 2016-1. The six classes of notes - which allow for the sale of a US$200 million tranche, if the demand is there - have been assigned preliminary ratings by Standard & Poor's Ratings Services and Fitch Ratings, respectively, as follows:Class      Rating                         Amount            (S&P/Fitch)                    ($million)A1      AAA (sf)/AAA(EXP)sf       US$200.0*A2      AAA (sf)/AAA(EXP)sf         A$164.3   AB      AAA (sf)/AAA(EXP)sf           A$21.5B         AA (sf)/Not rated              A$14.5C           A (sf)/Not rated                A$6.0D       BB+ (sf)/Not rated                A$5.0E               Not rated                     A$3.0(*Note: The notional exchange rate applicable to the class A1 notes is US$0.70 per Australian dollar, so the final dollar value of notes issued may change, depending on investor demand.)According to a pre-sale note from Fitch, the credit quality of the collateral backing the transaction - Resimac's first RMBS deal since August 2015 - differs in several aspects from prior pools of mortgages securitised under the Resimac programme. "The pool has increased investment and interest-only loans and [with 34.3 per cent LMI cover] is the first Resimac pool without 100 per cent lenders' mortgage insurance cover," Fitch noted.According to the Fitch pre-sale report, the average current loan size is A$395,894. Interest-only loans represent 55.6 per cent of the pool by balance, co-incidentally mirroring the proportion (55.3 per cent) of investment loans.Other characteristics of the collateral pool, as outlined by Fitch: The weighted-average seasoning of the portfolio is 16 months; with a weighted-average indexed loan-to-value ratio of 67.6 per cent.