A perfect bag with as many pockets as you need. It is fine as a carry-on with all the airlines I have used.

Quality construction with many pockets, practical for some, but definitely adds weight compared to the Cabin Zero which is also larger. Now it depends on each person how many days they are leaving for and how many things they plan to take. Personally, for a week I find it suitable, while for more days I would choose another one.

It is quite heavy and has a height of 53 cm, which means that it does not meet the requirements of some airlines that specify dimensions of 40x30x20 cm for carry-on luggage with a cheap ticket. Here I would like Skroutz to add additional filters for selecting a backpack when it will be used as carry-on luggage on airlines, as it has in the search for Travel Suitcases where there is a separate filter "Airline" with the explanation: Compatible Airline: Suitcases with the appropriate dimensions to be allowed as carry-on luggage in airline cabins.

Very sturdy with infinite compartments and pockets for everything.
Durable materials.
It seems that a lot of thought and work has been put into its design.
I managed to tear a small internal pocket with a laptop, but we stitched it up.
However, it's not the bag's fault, it's my fault for overfilling it like a savage.
It has a pocket for an umbrella and comes with a toiletry bag and an orange waterproof cover. It also has reflectors if you use it with a motorcycle at night.
It is also exactly the right size for cabin luggage on airplanes, and its main compartment is like a suitcase where you can also tie your clothes to keep them from getting wrinkled.
Super affordable price!
Wow, very impressive!

The bag is very big, resulting in it being heavy. For the trips I tried it on, my back got tired.

It is aesthetically beautiful, made of durable material, and has a lot of compartments. However, as it fills up, it becomes increasingly burdensome for the shoulders, neck, and back. I bought it as a second "hidden" cabin bag, but: 1) it was very heavy as I filled it to keep the bag at 8 kilograms, 2) the height is excessive and it takes an irregular shape on the back (it bulges upwards), 3) it does not fit fully under the seat, especially if it is very full (fortunately, no relevant observation was made). It fulfilled its purpose in any case, but with the feeling of a tiring experience!

Excellent build quality from Polo. It fits everything for a 3-day trip and has all the convenient compartments to keep things organized properly. It also comfortably passed as a backpack so far on Aegean, Ryanair, and EasyJet, so you are covered and don't need extra expenses. Not to mention, if you manage to get it inside the plane, you can easily place it in the overhead compartment because from a distance it looks like a small suitcase, so no one ever told me to put it under my feet! Win-win!

I used it on a two-week trip abroad for two people and I must admit that it exceeded my expectations! It has plenty of space to the point where you forget what you have put in it and it is lightweight on the shoulders. It is very helpful that it opens from the sides and becomes a small suitcase, but since it is a backpack, you always have it on you without being particularly bothered.

I don't think anyone needs to look further when it comes to functionality, ergonomics, comfort, and quality. It truly has it all! I frequently travel on trips ranging from 2 to 6 days and I have never encountered any problems. It fits everything, has a laptop compartment, and can also be used as a handbag when you hide the shoulder straps in their special compartment. It also has a phosphorescent waterproof hood in a special pocket. And finally, yes. It fits under the front seat of the aircraft, even if it is overly full. However, it does stick out a bit in length, but that's not a problem. The bigger issue is how to maneuver it between the seats to fit it underneath.
In conclusion, it goes without saying that it is not suitable for hiking, etc., but it was not designed for such purposes.
edit 1
The shoulder straps are not as comfortable for prolonged use. Of course, it also depends on the total weight that one has loaded onto the backpack.

Very good quality. It is indeed 40 liters. The zipper is of very good quality. It also has a special compartment with a waterproof hood to cover the entire bag in case it rains. It has a USB port for a power bank. And the laptop compartment can actually fit up to 17 inches and is isolated with a zipper, not in the same area where the travel clothes go.