Time to pack your shit - we gotta go! When you need the freedom to move your arms because you're running from a burning gasoline refinery, or just kicked in the paper door to a level 17 Kung Fu master's dojo, know that you'll have the free range of motion you need to lay the smack down on that MF'er. 

If anyone tells you that "backpacks are for kids" punch them in the face.