Double-walled lightweight thermos: The GSI MICROLITE 350 FLIP has a push-button operated hinged lid on the top. The incredibly thin two-millimetre walls, which are thinner than most single-walled plastic bottles, keep the drink cold for up to 8 hours and warm for up to 16 hours. Excellent for various occasions. The innovative system of opening the lid while drinking ensures maximum speed and ease of operation.