A device for producing multi-layer composites made of thermoplastic materials, including a coextrusion adapter through which the thermoplastic materials can flow. The adapter has an inlet opening and an outlet opening, in which the thermoplastic materials are combined in layers. The coextrusion adapter has a modular design including a plurality of housings stacked on top of each other in a modular manner, each having a central channel arranged in the housing and at least one coextrusion channel opening into the respective central channel. The central channels of the housings stacked on top of each other continue one another, and the thermoplastic materials can flow through the central channel and the coextrusion channels in the direction of the outlet opening. Each housing further includes a receiving bore that extends through the central channel and into which a coextrusion pin can be inserted, which in turn has a channel bore that continues the central channel and in some regions forms a partial section of the at least one coextrusion channel between the outer surface and the wall of the receiving bore.