According to the different volume of the backpack, the backpack can generally be divided into three categories: large, medium and small.

Large backpacks with a volume of more than 50 liters are suitable for medium and long-distance travel and more professional adventure activities. For example, when you are going to a region like Tibet for long-distance travel or mountaineering expeditions, you should undoubtedly choose a large backpack with a volume of more than 50 liters. Some short- and medium-term trips also require large backpacks when camping in the wild, because only it can hold the tents, sleeping bags and sleeping pads you need for camping. Large backpacks can be divided into mountaineering bags and long-distance travel backpacks according to different uses.

Mountaineering bags are generally slender and long in order to pass through narrow terrain. The bag body is divided into upper and lower layers, and the middle is separated by a zipper interlayer, which is very convenient when picking and placing items. The sides and top of the backpack can be tied with tents and cushions, which virtually increases the volume of the backpack. There is also an ice axe cover outside the backpack, which can be used to bundle ice axe and snow poles. The most worth mentioning is the back structure of these backpacks. There is a lightweight aluminum alloy inner frame that supports the bag body. The shape of the back is designed according to ergonomic principles. The back is wide and thick, and the shape is in line with the physiological curve of the human body. "S" shape design, and there are chest straps that prevent the straps from sliding sideways, making backpackers feel very comfortable. And all of these packs have a sturdy, wide and comfortable waistband that can be adjusted in height. Users can easily adjust the straps to their own height according to their body shape. Generally speaking, the bottom of the backpack is above the hips, which can transfer more than half of the weight of the backpack to the waist, thereby greatly reducing the burden on the shoulders and reducing the damage to the shoulders caused by long-term load.

The body structure of the long-distance travel backpack is similar to that of the mountaineering bag, except that the body is wider and equipped with many side pockets, so that the scattered objects can be sorted and placed.

The volume of medium-sized backpacks is generally between 30 and 50 liters. These backpacks are more widely used. For 2-4 days of field trips, travel between cities and some long-distance non-camping self-help travel, medium-sized backpacks are more suitable. . The clothes and some daily necessities that you bring with you can fit. There are more styles and types of medium backpacks. Some backpacks have added side pockets, which are more convenient for packing items. The back structure of these packs is roughly the same as the larger packs.

The volume of small backpacks is less than 30 liters. These backpacks are generally used in cities. Of course, they are also very suitable for 1-2 days of outings.