Nathan Hydration backpack holds 3L bladder but that’s NOT included. Has ample storage space holds the bladder in an insulated zippered compartment to keep fluids cold, adjustable side straps to customize and conform the pack to your torso. See pics for the details and measurements; the shoulder/torso straps forms and “X” on the front of the chest to take pressure off the shoulders and helps stabilize the pack on your back.