The Chill-Its 5051B Three-Liter Replacement Bladder is compatible with the 5156 and 5157 Hydration Packs (sold separately). The bladder features a DualCap for easy no-spill filling with water or ice, plus an insulated tube to keep water cool in the heat. Capacity: 3 L. For Use With: ergodyne® Chill-Its 5156 and 5157 Hydration Packs; Color(s): Blue; Color Family: Blue; Material(s): Thermoplastic.