After much research, I ended up getting the 65-liter Atmos backpack and it is truly PERFECT. I used it for a 3-day trek initially and then a 7-day trek, and I have nothing negative to say, on the contrary, I am thrilled.

POSITIVES:
- Huge spaces
- Endless pockets, compartments, etc. Everything finds its place.
- Clever special compartment for a sleeping bag
- It doesn't tear at all.
- It inflates, stretches, fits everything, and by using the external straps, you can attach a sleeping pad, tent, shoes, etc. on the outside.
- I used the rain cover, and it works perfectly. It was easily placed and even in heavy rain, not a drop passed through to the backpack, nor did the exterior get wet.

POSITIVES:
- Waist strap pockets with zippers. You can put your phone, wallet, keys, snacks, camera - it holds a lot and you can easily grab them with just one hand.
- AMAZING fit on the back and waist. It's magical to have a weight of 10-15 kilograms on your back and not feel it at all. If you pay attention to the fit on your back and properly tighten the waist and chest straps, you truly forget that you are carrying such weight.
- Nice diagonal pocket for trekking poles that holds them in place with a cord, and on both sides, it has special plastic to prevent slipping. In the lower pocket, I hung damp shirts or fleeces soaked with sweat or rain to dry while walking - thanks to the special plastic of the pocket, there is no chance they will fall down.

EXTREMELY POSITIVE: The bottle pockets have two openings, one large horizontal and the other (the important one) is diagonal so you can grab the bottle while moving and easily put it back. A fellow traveler with the same backpack hadn't noticed it, so check it out if you buy it - it's a lifesaver because you don't have to stop and take off your backpack to take a sip of water, as is the case with most backpacks on the market. You take out your bottle effortlessly, drink, and put it back in the diagonal pocket without any hassle.

- I got the 2023 version, which solves the problem that was attributed to the previous version: that the backpack has a tube-like shape and to reach an item that you had placed at the bottom, you had to empty and refill it. In the new version, there are vertical zippers on both sides that open the backpack along its entire length, allowing you to directly reach items you have placed inside anywhere - even at the bottom - without having to empty it.

Now, let me mention a FEW NEGATIVES:
- The zippers on the two small pockets on the waist strap are stiff, making it difficult to open and close them with one hand. It's a minor detail, but when you hike for hours and just want to grab your phone for a quick photo, it becomes tiring to struggle with the zipper.
- The "clasp" - the part of the backpack that you lift up and down to open and close it - is a bit poorly designed. It doesn't stretch well, resulting in it not fitting properly and closing crumpled. I can't exactly explain what happens, it just doesn't stretch correctly. The only solution is to fill the two back pockets (with zippers) with something that takes up space (hat, shirt, large pack of baby wipes, etc.) so that it expands and fits properly when closing the backpack.

Overall, I am very satisfied and seeing other friends' backpacks, etc., I realize that this particular backpack is by far the best in its category and for its price.