Brakes, the Xte

Moin, picked up my Volvo 850 T5r yesterday ( Finally I have a…. ) I read and read, don’t get quite smart: brake discs 280mm – others say the R have 305mm. Does this apply only to the 850R or also to the T5R Should it mean that I have 280mm in it – which normal tenure, for students affordable brake combination has proven itself by now ?