I too want to purchase but,"Medium fits an 18" to 20" torso and the large fits a 20" to 22" torso!"What do these measurements measure?
SunnySports S They measure the length of your back along the spine to insure the pack is not too big or too small. Here is how to measure: Using a flexible tape measure, measure the length of your torso from the C7 vertebra (at the base of your neck) to the spot on the spine level with the top of the bony hip structure called the iliac crest. Do it two or three times to get an accurate measurement. If you are between frame sizes, always go with the smaller size.