The invention relates to a spinneret for spinning thermoplastics. Said spinneret comprises a central polymer inlet channel, a filter assembly (2), consisting of one or more filter plates of various filtration grades, a spinneret plate (3) and a housing (1) which receives and tightly surrounds the filter assembly (2) and the spinneret plate (3). The selection of suitable materials and tolerances for the individual parts of the spinneret enables the sealing effect to be achieved at operating temperature by the increased expansion of the internal components, in relation to the external housing.