Please tell me how to choose a backpack for long-distance travel:

First, you have to decide what size bag to buy. The capacity of internal rack bags generally ranges from 40-120 liters. For the average traveler, a 65-75 liter bag is sufficient for most long-distance trips. If you need to camp in the wild for a long time, if you are a die-hard outdoor sports person, or if you often move when you go out, you may need a 120-liter one, haha.

To be honest, most people will not need a bag exceeding 100 liters. Moreover, in theory, each person should only carry a maximum of one-third of his or her own body weight. If you pack too much stuff, only you will know how painful it is when you carry it. So, it's better to take it easy.

When buying a bag, you should not just look at the capacity and number, but also the size of the suspension system you should use. Before choosing a bag, you'd better ask family and friends to help you measure your torso length (torso length) with a ruler (preferably a tailor's tape measure). This torso length refers to the distance from your seventh vertebra (the most prominent bone at the junction of your neck and shoulders) to the vertebra parallel to your hip bone. This torso length needs to match your inner frame. Don’t think that you should carry a large bag because you are 1.8 meters tall. Some people have long bodies and short legs, and some people have short bodies and long legs.

Generally speaking, if your torso length is less than 45 cm, you should buy a small size bag. If your torso length is between 45-52 cm, you should choose a medium size bag. If your torso length is over 52cm, you should pick a large size bag.

Good manufacturers provide extra large (over 56 cm) or extra small (under 40 cm) bags, and they can also be customized. Bags from major manufacturers vary in size, and even different series of bags from the same manufacturer have different sizes. You'd better ask for clarification, or find some information. If that doesn't work, just measure the length of the inner shelf.