NylonINSULATED BLADDER COMPARTMENT: This hiking hydro backpack has a special separate insulated compartment for the water bladder to keep liquids cool for up to 6 hours (with ice packs), making it perfect for long hikes, bike rides, or any outdoor adventures.ImportedHIKING/CYCLING/RUNNING/SKIING WITH EASE: This 2 lbs lightweight water backpack features an ultra-elastic 3D breathable padded back, adjustable chest and waist straps to provide comfort and stability for all body sizes. This day pack has got you covered for all your adventures.UTMOST STORAGE CAPACITY: Backpack size 18.5" x 10.5" x 6". Stay organized with 9 functional divider pockets to keep all your essentials secure. The 18-LITER main compartment is large enough for clothes, notebooks, first-aid kit, pet supplies. Built-in mesh pocket for personal valuables. Exterior upper velvet pocket for protecting glasses, cameras, cell phones. Trekking poles/water bottles fit in the side mesh pockets for easy access.EFFICIENT HYDRATION SYSTEM: This 18L hydration backpack includes an UPGRADED 100 oz / 3-LITER water bladder made of FOOD-GRADE PEVA material. The water Pouch has a Large Opening for easy refilling with water, ice cubes and cleaning. The high-flow bite valve is ergonomically designed for more comfortable use. The mouthpiece cover protects the bite valve against dirt and damage.SECURE YOUR ADVENTURE: The hiking bag features High-Density Nylon fabric and a Built-in Rain Cover - ideal for rainy activities. The reflective strips keep you visible in low-light conditions. A designated space for your helmet between the outer and middle pockets.