One day walking backpack: usually single-day walk will carry a simple wind and waterproof clothing (winter to bring spare cold clothing), first aid kit, stove pan pan, a meal of food and some energy small food, kettle and water, Spare headlights or flashlight and electronic entertainment products, etc., depending on the volume of the items, these items need about 18 liters or so -35 l capacity backpack. If you need camping, in addition to the above items also need to carry tents and sleeping bags, which requires about 35 liters ~ 45 liters quick release bicycle handlebar phone bag.