The Flip Cap provides a narrow-mouth spout for on-the-go drinking. The medical-grade silicone flip top seals with the polypropylene (PP#5) cap. The pivoting handle provides a great way to carry the bottle and stows out of the way while drinking. Wide-mouth access makes it easy to add ice cubes or fresh fruit. Slim and mobile. The 475ml travels wells and looks great doing it. The silicone flip top seals when plugged but is not upside-down, bottom-of-the-bag leakproof.