Abstract: A thin slab nozzle comprises: a central bore defined by a bore wall and opening at inlet orifice and extending therefrom along the longitudinal axis X1 until it is closed at an upstream end of a divider, said central bore comprising: an upstream bore portion comprising the inlet orifice and extending over a height, Ha, and, adjacent thereto, forming an upstream boundary with a converging bore portion of height He located in the connecting portion of the thin slab nozzle, and adjacent thereto a thin bore portion of height Hf located in the diffusing portion of the thin slab nozzle and ending at the level of the upstream end of the divider, first and second front ports separated from one another by said divider and coupled to the central bore portion at least partially at the converging bore portion; characterized in that, in a section of the thin slab nozzle along the first symmetry plane ?1 defined by (X1, X2) wherein X2 is normal to X1, the geometry of the wall of the central bore is characterized as