Hydrapak Wooly Insulated Bottle, 21-Ounce Double-walled construction layered with PRIMOLOFT insulation High-flow Mammoth Valve constructed from soft Thermoplastic Elastomer (TPE) Gripper cap with tall sides for easy opening/closing Resilium Polypropylene technology for durability, flexibility and light weight Dishwasher safe (top rack)/Freezer safe