The volume of pack needed by different people for a certain length of trip varies considerably between individuals depending on gear choice and is also affected by the season and the terrain. Packing your gear in a pack of known volume is a good way to determine your volume requirements. Note that the Ultralite family includes the Balance Pockets as standard, therefore the specified volume is with the Balance Pockets.
With the Daylites, Stronglites and Travelites, the volume specified is only for the pack itself, so adding your choice of Balance Pockets or Bags will increase the total volume accordingly. Therefore you need to add the volume of the Balance Pockets or Balance Bags to the volume of the pack to get the total volume to match your requirements.
Now consider the longest trip you will do with the pack and the gear required. This will determine the volume of pack needed. Now think about the predominant use and choose the most appropriate family for your needs.
NOTE: We strongly recommend using Balance Pockets or Balance Bags in all situations except technical climbing. They will reduce energy use and body pain compared to carrying all your load behind in a backpack. The instant gear access of the pockets also increases efficiency, as you do not have to stop and take the pack off to access items needed during the day. Specific purpose Balance Pockets, Bags and clip-on accessories allow you to customise your pack for different activities.
Based on your backlength and the volume you require, you can see in the chart below what models will work for you. To further refine your selection, you need to take into account your activity and the sort of country you will be using the gear in.