OMM Ultra Flexi Flask 350ml with Straw - SS19 Polyurethane (TPU) construction - Durable Thermoplastic with extra grip. Flexible / squeezable - Lets you easily squeeze out gels or liquids. Compresses as you drink - Reduces sloshing/bouncing of fluids. Fill scale - Helps you monitor fluid intake (ML and OZ). Slim and lightweight, easy to fill and clean with wide opening