The side pockets are very deep (almost 30 cm high) and each has a drawstring. So, unless you store a 1 liter bottle in it, it's a bit disproportionate for the use I usually make of it. On the other hand, it is practical for storing a rolled up magazine, a baguette or other fairly long objects and the cord clamp allows the contents of the pocket to be pressed against the bag. I had not found any information on the back before buying my bag. That's why I show you some pictures, I was pleasantly surprised to see that the back is straight and that inside a perforated foam allows a good compromise between ventilation and comfort. The perforated foam is protected by a breathable mesh fabric. It is sewn on the back with a bias, which reinforces it in the most stressed places. As with any self-respecting hiking bag, Topo has thought of putting a sternal strap, as well as a belt, a minimum to maintain good stability during your travels.