Gossamer Gear "G4-20" 42L pack

An ultralight, frameless 42L pack. 

weight: 22oz/627g

Sizing - measure from your C7 vertebra (big bump on back of your neck) to your iliac crest (top of your pelvis/hip bone)

Small Size fits:
Torso - 11.5" - 15.5"
Hip - 25" - 35"

Medium Size fits:
Torso - 15.5" - 19.5" 
Hip -  30" - 42" 

link to product listing on Gossamer Gear site