I have the 44Ltr as a daysack - It
DOES have an adjustable back system, in so far as it's possible to adjust the position of the shoulder yoke up or down the body of the pack. Not as infinately adjustable as the larger models but certainly adjustable enough to adapt it to the length of your back. I find it very comfortable; even when I have it fully loaded for a weekend in the woods (48lbs worth of gear, inc 6 litres of fresh water!). One thing to watch though is the buckles on the hip belt, they easily slide off the belt when you take the rucksack off and are moving it around. I nearly lost the male part of the buckle this weekend - problem cured by putting a safety pin through the end of the belts to stop the buckle slipping off!