The Hydrapak Wooly Mammoth lives up to its name of keeping your drink the temperature you want it for longer whether that be hot or cold and it keeps liquids from freezing when temps drop. This advanced water bottle includes the proven insulation, Primaloft between its double walls to create the most advanced insulated sports bottle on the market. Tests with leading brands are no match for the performance shown for keeping the temperature stable in hot or cold conditions. The Wooly also uses polypropylene, a lighter weight more flexible material along with a large spout for maximum flow rate. Polypropylene bottle with resilium technology Expedition quality primaloft insulation Mammoth drink valve Gripper cap Material: lightweight, BPA free polypropylene Size: na Weight: na Capacity: 20 oz.