The paper deals with the design and optimization of an extrusion die which consists of a die body and a set of replaceable plugs for various extrusion cross-sections. This system is primarily used for producing WPC products on the laboratory extruder EUROTECH EB30. The paper offers several designs of extrusion dies and examines their advantages as well as disadvantages. Based on this analysis, the best design is chosen and then flow simulations through a die and by FEA are done.