Mortgage lender Firstmac will pay 160 basis points and 210 basis points over swap on the respective top two tranches of its latest issue of residential mortgage-backed securities.On Friday, Firstmac placed A$300 million of notes, the 1-2012 Residential Mortgage Backed Securities Issue. It will pay 160 basis points over the 30-day bank bill swap rate for the $144.5 million A1 tranche, which has a weighted average life of 1.4 years.And it will pay 210 basis points over the 30-day bank bill swap rate for the $131.1 million A2 tranche, which has a weighted average life of 6.1 years.Pricing on the $13.4 million AB tranche, which has a weighted average life of 6.1 years, is 300 basis points over swap. Pricing on the $9.25 million B1 tranche, which is rated AA, was not disclosed.The Australian Office of Financial Management bought $129.1 million of the A2 notes and all of the AB notes.Firstmac's chief financial officer, James Austin, said seven real-money investors had bought a total of $121.2 million of notes in the issue.Austin said: "This transaction [is]...among the highest level of managed fund participation of any Australian RMBS transaction in recent years."