The QuaDrum rigid outer containers (ROCs) from Meissner are used for rehydration and mixing applications. The retaining lid, stainless steel dolly, and bottom drain allow recirculation-based mixing for process volumes between 50 L and 200L. The retaining lid for mixing applications provides access to fluid paths located on the top of the biocontainer and can positively locate and support a 3-inch TC port on top of the biocontainer. This port can be used for powder addition or other operations that require large bore access to the biocontainer. The stainless-steel dolly, which is required to facilitate bottom drain applications, can be specified with swivel wheels that lock for added security.