The Alice Pack was the US military answer to modularizing a soldiers field gear, in that the main pack and web gear could be two separate components. In WW1 and WW2,the haversack designs did not allow an infantryman many choices, he either had all his gear or none, pretty much. The Alice Pack was widely used in Vietnam. The main bag compartment is about 1500 cu in, with another 3 exterior pockets that are very usable in size. A very well thought out and proven design.