[pct-l] Backpacks, which size is best?

[ambery-80243 at mypacks.net]

The suggestion about knowing what kind of gear you will have first and then trying packs is great advice.
You also need to look at your personal preference for carrying gear.  I have heard people say they do a whole long trip carrying a 45L pack, but they may or may not have lots of stuff hanging on the outside.  I personally like my gear to live inside the pack, so I may take a 60L for the same trip so that I don't have things dangling outside my pack.