slipring

1) identifies the need for bag sizes (backpack size)
Backpack size or capacity, we usually use liters (l) units, some countries also used cubic inch (CU IN) a unit (about 1000 cubic inch 16 litre).
45L: this capacity suitable for use by women, and in the warm season of good weather 1-2 days of camping and hiking. Can also be used as base camp activities or hiking around hoisting packages.
50-70 l: in spring, summer and autumn seasons can be supported long travel and hiking, can be filled with warm clothing, tents and other equipment and more food. This capacity is more than that.
70-95: If you're a man, and decided to just buy a package, you can select this range. This capacity should be able to cope with all the equipment needed in winter, and is also suitable for long, long journey.
More than 95 l: these mammoth monsters can cope with outdoor activities and traveling for a long time, especially in the winter and mountain expeditions of exploration, to the base material is also suitable for bad luck. Or maybe a very strong person led a few mm, but carry major equipment.