The MSR DromLite Bag - 4L offers high-capacity water storage yet collapses all the way down to the size of the cap. This supreme packability comes with the weight savings to match to keep you moving quickly on the trail. It is constructed of a rugged film and RF-welded seams, they offer reliable durability. Inside, an improved BPA-free food-grade lining ensures better-tasting water and can handle freezing. The svelte 3-in-1 cap lets you fill, drink and pour with ease.