Double wall vacuum cleaner, both the inner and outer walls are made of 100% food grade 304 stainless steel. Let the beverage cool for 24 hours and heat for 12 hours with our double wall vacuum insulation technology, keeping your beverage as it is! Whether you are exercising outdoors, at school, or working indoors, you can enjoy cold or hot drinks all day long! 2.7cm L x 2.7cm W x 10.6cm H