Slab nozzle for casting slabs made of metal, said slab nozzle having a geometry defined by an outer wall extending over a nozzle length, L, along a longitudinal axis, z, from an upstream end to a downstream end, said outer wall comprising a downstream portion extending along the longitudinal axis, z, from and including the downstream end, wherein • the upstream end of the slab nozzle comprises an inlet orifice oriented parallel to said longitudinal axis, z, and wherein • the downstream portion of the slab nozzle comprises one or more outlet port orifices, said downstream portion being defined by a width measured along a first transverse axis, x, which is at least 1.5 times larger than a thickness of the downstream portion measured along a second transverse axis, y, wherein the first transverse axis, x, is normal to the longitudinal axis, z, and wherein the second transverse axis, y, is normal to both first transverse axis, x, and longitudinal axis, z, said slab nozzle further comprising a central bore opening at said inlet orifice, extending therefrom along the longitudinal axis, z, and intersecting one or more front ports each opening at the one or more outlet port orifices, characterized in that, in a cut view of the slab nozzle along a transverse plane, P3, the outer wall of the slab nozzle is defined by an outer wall outline which comprises: • a central portion ( Ax) wherein the outer wall outline is symmetrical with respect to a central point, c, defined as the intersection point between the longitudinal axis, z, and the transverse plane, P3, and is preferably symmetrical with respect to both first and second transverse axes, x, y, and said central portion being flanked by • a first and second lateral portions ( Ac1, Ac2), positioned on either side of the central portion ( Ax) along the first transverse axis, x, and wherein the outer wall is symmetrical solely with respect to the central point, c, • the outer wall outline of the downstream portion is inscribed in a virtual rectangle of first and second edges parallel to the first transverse axis, x, and third and fourth edges parallel to the second transverse axis, y, and wherein a tight distance, dt, of the outer wall outline to first and second diagonally opposed corners of the four corners of the virtual rectangle is at least 1.5 times shorter than a flared distance, df, of the outer wall outline to the other two diagonally opposed corners of the virtual rectangle, wherein the distance of the outer wall outline to a corner is defined as the distance between said corner and a point of the outline located closest to said corner, wherein the transverse plane, P3, is the plane normal to the longitudinal axis, z, and intersecting the one or more outlet port orifices, which distance, L3, to the downstream end is the largest. • the upstream end of the slab nozzle comprises an inlet orifice oriented parallel to said longitudinal axis, z, and wherein • the downstream portion of the slab nozzle comprises one or more outlet port orifices, said downstream portion being defined by a width measured along a first transverse axis, x, which is at least 1.5 times larger than a thickness of the downstream portion measured along a second transverse axis, y, wherein the first transverse axis, x, is normal to the longitudinal axis, z, and wherein the second transverse axis, y, is normal to both first transverse axis, x, and longitudinal axis, z, • a central portion ( Ax) wherein the outer wall outline is symmetrical with respect to a central point, c, defined as the intersection point between the longitudinal axis, z, and the transverse plane, P3, and is preferably symmetrical with respect to both first and second transverse axes, x, y, and said central portion being flanked by • a first and second lateral portions ( Ac1, Ac2), positioned on either side of the central portion ( Ax) along the first transverse axis, x, and wherein the outer wall is symmetrical solely with respect to the central point, c, • the outer wall outline of the downstream portion is inscribed in a virtual rectangle of first and second edges parallel to the first transverse axis, x, and third and fourth edges parallel to the second transverse axis, y, and wherein a tight distance, dt, of the outer wall outline to first and second diagonally opposed corners of the four corners of the virtual rectangle is at least 1.5 times shorter than a flared distance, df, of the outer wall outline to the other two diagonally opposed corners of the virtual rectangle, wherein the distance of the outer wall outline to a corner is defined as the distance between said corner and a point of the outline located closest to said corner,