FirstMac on Friday launched a refinancing of its FirstMac Bond Series 1C -2006 Trust that comprises prime, low-doc, mortgage-backed securities. The original A$354 million Class A tranche was subject to a December 2009 call option. The 23 basis point spread on the tranche doubled when the call option was not exercised.FirstMac decided it was better for investors and itself to exercise the call option and refinance the tranche. Accordingly, it will now raise A$350 million via FirstMac Bond Series 1C -2006 Trust (2010 Notes). The issue will comprise four tranches: A$297 million of 'AAA' rated Class A notes with a WAL of 2.4 years; A$36 million of 'AAA' rated Class B notes with a WAL of 3.9 years; A$9 million of 'AA-' rated Class C notes with a WAL of 3.9 years; and A$1 million of unrated Class D notes.The notes will price next week with an indicative spread of 140 bps to 145 bps over bank bills for the Class A tranche. The higher than usual margin is due to low-doc mortgages making up around 16 per cent of the underlying mortgage pool.