1 kg, 36L, 48x34x22 cm (couldn't find this bag at some english site)
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Pro Nice amount of compartments
Allows to keep things organized while keeping it lightweight (just 1 kg). If it had too many things built in it would get heavier thus taking away room from how much you can stuff in.
Pro Good size for airplanes
It's very unlikely any company will ever refuse you to take this as a hand luggage now or any time in the future.
Pro Can be reduced
If you don't add much, it will get smaller.
Con Not water proof
It probably won't take much rain or save anything inside if it fells down into much water.
Con Won't expand beyond 33L
It should be able to get to 40 maybe 50L and still be all right for most airlines today.