During my trips I realized that there some gadgets without which you should never leave home. I am not a brand fan but I have strong reasons why I added the brand itself to some of the items, they do make a difference (I tried others before).
It does not have an official carry on size, but if not overloaded you can pas with it at airlines that have hand-luggage + accessory. I had no issues on Iberia and Brussels Airlines. I have the S size. The way the back pack is made is very convenient (opening as a normal luggage) and the small backpack can be used on any trip as a perfect day-pack.