If a shorter travel time (1-3 days), and was not prepared to outdoor camping, carrying goods is not much, should choose small volume of the backpack, generally 25 to 45 liters is enough.
如果出行时间较短(1 - 3天)，且不准备在户外宿营，携带物品不多，宜选中小容积的背包，一般25升至45升就够了。
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