Backpacks come in either external or internal frame designs. Internal types dominate in the market today, due to two main factors. Most-conspicuously, but functionally secondary, is the popularity (or more accurately, prestige) of mountain climbing, rock-climbing, ice-climbing & etc. More-pragmatically & realistically, the problem with external frame designs is that they really need to be custom-fitted & adjusted. Mass-manufacturing cannot address this need well, and the design still inherently places complexity-demands on the user, even when it is implemented well. … cont’d >