With the BOB (in a day sack) and the trauma bag on one side the rubber made container fits in with very little play. I cover it all up with 2 old army blankets. Not only keeps them from shifting a little, but hides the stuff and gives me 2 wool blankets. Normal FAK is a separte container stuck behind the trauma bag. Keep the usual tools, flares, oil, fluids, work gloves etc in the rubbermaid container.
Dave