Abstract: An ink supply for a printing system is disclosed which provides a high barrier to air yet is inexpensive to produce. The ink supply includes a chassis having a first and second protrusion. An aperture extends through each of the protrusions to allow fluid communication with a bag; the bag is attached to the chassis so that at least a portion of the first protrusion is surrounded by the bag. Embodiments of the supply include least one air barrier insert, located in the aperture; a septum located in the air barrier; a film attached to the second protrusion and covering the aperture in the protrusion; and a shell which extends around at least a portion of the bag.