The TD04 turbocharger used in Volvo models came equipped with 3 different exhaust outlet designs. Of these three (Conical, Straight, Angle) the Angle flange flows the best and is the preferred housing for performance and midrange spooling.
The Angle flange housing also came in two styles; 6cm^2 and the larger 7cm^2. The better flowing 7cm^2 features a more open inlet design as compared to the smaller 6cm^2 style housing.
** Note that if you're changing from either the conical or straight flange housing to the angle flange housing you'll want to make sure you have a matching downpipe connection! **