Part stuff sack part manly tote, se this as a dump bag for all your rounds and other odds and ends. Toss it into your ruck and go.
The Brick Bag was born years ago out of necessity. We always take inspiration from military gear and I had a similar sack back when I was in Iraq. Its original intent was as a carrying bag for the gear you would need in case of a biochemical attack, and it was to be with you at all times. By the time I made it over to the Sandbox, that was no longer required. But the bags remained with our team, so I used it as a stuff sack. As we at GORUCK are fond of doing, we trimmed down the excess to create the Brick Bag.