Made of Pro Grade 18/8 stainless steel. It is extremely durable, does not corrode or wear for years of continuous use. No leaks. Seals completely with the inner rubber on the cap. It does not sweat at the temperature difference. No more water on the table, no moisture in the bag, no slipping. Opens and closes with a single turn! Quick opening without leaks. Double wall thermal protection keeps the cold 24 hours and the hot 12 hours. Protection against odors and tastes thanks to its non-toxic construction materials. Large 33mm spout for quick filling. It also fits ice cubes.