The Wingnut lid is a unique twist on function. The two large openings make it easy to carry, while the wingnut like shape makes it easy to open and close effectively. It features 1-turn rotation which reduces the amount of turns needed to access your beverage. The Wingnut features a custom gasket which provides a perfect seal to all MiiR Bottles, leaving your bottle leak proof. The Wedge lid is made from polypropylene #5 which is BPA and toxin free and has been tested independently by SGS USA.