The oex drysac is an uber lightweight way to ensure your gear remains un soggy in tough conditions. No one wants their spare clothing to get wet and the waterproof, abrasion resistant fabric with fully taped seams will sit like a cacoon of dryness around your stuff, even in the pouring rain. This larger 40 litre bag is ideal for stashing your change of clothes or larger essentials essentially making your entire backpack a dryzone.