Blouch are notoriously bad at supplying turbo data on thier turbos. You kinda just have to look around and see what sort of results other people get with similar setups, and hope for the best when buying a Blouch. They dont specify the A/R, So I dont actually know the A/R of the turbo.
But the turbo i ordered is a DOM 2.5XTR with 10cm^2 turbine housing and 3inch compressor housing.
This is the Blouch description of the turbo.
Subaru WRX/STi Dominator 2.5XT-R "Polka Pickle" Ball Bearing Turbocharger