Berghaus's own Freeflow harness system allows air to flow past your back, keeping you cooler whilst walking.  The shoulder straps can be adapted to fit different length backs, and there are 3L expansion pockets on both sides making up the additional 6L capacity.  The main compartment has a pocket for up to 2L hydration packs, and there's even a rain cover neatly hidden away.

Materials: Ardura 420, DuPont 700D Cordura
Capacity:25+6L
Weight:1.5kg
Size:adjustable