I like using something similar when I am traveling..can put in a lunch, camera equipment etc when you go for hikes...personally, I have found, mainly because I usually take way too much stuff..a like wheels for my carry on..with the books, optics, travel doc, money, etc..gets way too heavy to cary on my should all over the airport.which I usually also put in one day of change of clothes as well in case my luggage doesn't show up....but that is usually only on travels to the other side of the planet..otherwise..the one shown is my perference as well..

Ripp