Abstract: A spinneret assembly is disclosed that comprises thin individual spinnerets simultaneously exhibiting a great mechanical resistance to pressure and a great number of orifices, in which:the relation between the total piercing area and the total surface of the assembly is between 35% and 90%;the relation between the total number of orifices and the total surface of the assembly is between 0.2 and 25 orifices per mm.sup.2 ; andthe relation between the total surface of orificesand the surface of the assembly is between 0.5% and 40%; the spinneret assembly comprising a rigid supporting plate pierced with holes designed for the passage of the spinning material, every hole being coaxially associated with an individual spinneret and having at least one portion the cross sectional area of which is less than that of the surface of the respective spinneret.