The older version's are not able to adjust for Torso length (at least mine does not). That may or may not be a problem. When I wear the j104 or my new jp9 they feel weird at first (much different than my 4500), but I don't get any pain in my neck, back, or shoulders carrying loads in them or just carrying it around on my back all day. If the J104 fits you when you get it, it is a nice pack to have.