When selecting a Backpack
When choosing a new pack consider:

• Trip length for sizing:
  • Daypack: 2200 cu. inches or less
    
  • 2-3 Days: 2200 - 4000 cu. inches
    
  • 4+ Days: 4000 cu. inches or more
  
  
• Internal frame, external frame, or frameless
  
• Fit for optimizing comfort and function
  
• Weight distribution of the pack
  
• Hydration bladder compatibility & other features

Internal frame packs are the dominant choice for backpackers. These packs keep the center of gravity close to the user's back. An internal pack has its frame inside the pack (members of the frame are called stays). Ultralight backpackers select frameless packs to reduce weight.
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