Mountain Hardware Wayback 30 Backpack Size Chart
  Small/Med Med/Large
Torso Fit Range (in) 16-19" 18½-22"
Waist Fit Range (in) 28-34" 33-39"
Capacity (cubic in) 1850 2075
Product Weight 2 lbs, 9 oz 2 lbs, 12 oz

These are general guidelines only, sizes are not guaranteed. But no worries, since at SunnySports we offer our exclusive PFF Guaranty