Abstract: To provide a disposable container which can be prefabricated under sterile conditions, a pair of concentric plastic rings are formed with interfitting, interlocking projection and recess means permitting the rings to be snapped together, the rings being additionally formed with matching fitting surfaces to interpose the edge portion of a gas permeable membrane therebetween so that, when the membrane is placed on the outer ring and the two rings are snapped together, the membrane is irremovably held. Preferably, the outer ring is made of a softer, yielding plastic, the inner ring of a more rigid plastic, with a projection snapping into a groove formed on the inner, more rigid ring, and the matching clamping surfaces for the membrane forming a sinuous, tortuous path with a flexible projecting lip on the outer ring fitting into a recess to clamp the membrane and seal the membrane in the structure.