HYDRO FLASK PRISM POP 21 ounce STANDARD MOUTH BOTTLE WITH BOOT :: Stay hydrated and catch some eyes with the new Hydro Flask Prism Pop 21 ounce Standard Mouth Bottle with Boot. With a unique double wall TempShield(TM) vacuum insulation cold drinks keep chilled and hot ones stay piping hot for hours of enjoyable refreshment on the go. Made of 18/8 pro-grade stainless steel a stylish boot offers extra protection from bumps and spills.