The Mystery Ranch Urban Assault 18 Pack is a slightly smaller version of its original big brother pack, the Urban Assault 21. This newer model maintains the 3-ZIP design but in a package three inches shorter and three liters smaller than the original. The bag includes an HDPE frame for support and rigidity and fixed harnessing. It also has two zippered interior pockets and a sleeve for up to a 15-inch laptop. This newer version includes a volume of 1,100 cubic inches, which still offers ample storage.