The present invention includes a disposable flow path for an infusion system for communicating between a fluid source and a patient. The flow path comprises a flow restrictor having first and second ends and defining a flow path between the ends. The flow restrictor comprises a plurality of materials, including a first material defining the flow path, which first material is substantially resistant to vapor transmission, and a second material different than the first material defining at least a portion of an outer surface of the flow restrictor. The second material is suitable for joining to other portions of the flow path.