I wanted a day pack that was truly water-proof but also holds enough gear for short overnight hikes. This is it! I Love the advanced composite material (foam impregnated fabric ) it is tough, ( we now build airplanes with this technique) lite wt. durable and totally waterproof. Filled with 22lbs, I tossed the pack in my swimming pool and it not only floats but all my gear stayed totally dry. I use it for winter snowshoe treks, all-day rain treks in Scotland and have not had any moisture inside the pack. The only inconvenience is getting into and out of the pack quickly thru the roll top and bayonet fittings with the cover on. It is still my favorite pack ( I have four others). The Hybrid construction always draws OOOhhs and AAAhhs from my trekking companions.