Device for mixing medical fluids

A device and method for mixing medical fluids is disclosed. The device has an inlet port, an injection port, an outlet port, a first duct between the injection port and the inlet port, and a second duct between the inlet port and the outlet port. The injection port is sealed by a fluid-proof membrane which can be penetrated by an injection needle. The device further includes at least a first portion made of a first material and a second portion made of a second, substantially more resilient material, wherein the inlet port and the injection port are included in the first portion and the outlet port is included in the second portion, and the first and second portions are attached to each other by means of a combined friction coupling and snap connection.