This military style hydration backpack is constructed with rugged 800D oxford fabric and nylon lining. It includes a 3L hydration bladder / reservoir. It's extremely easy to fill and insert into the hydration pack or backpack. The large opening allows you to add ice cubes to keep your water cool for a long time. The SA-HP1 3L hydration backpack is the best choice to stay hydrated when you go outdoors for camping, cycling, hiking, biking or running, YOU WILL LOVE IT for sure. It is compact with 16.9" x 7.1" x 2.8" in size and 17.6 ounces in weight.