The Vacuum double wall was made of high quality grade 316 stainless steel that completely taste-free, rust-proof, leak-proof, The lid was made of food-grade silicone, BPA free, with an airtight silicone seal that prevents the drinks from spilling. Air Vent on the lid allows beverages to flow out smoothly, without gushing or overflowing.The rubber design at the bottom prevents the cup from slipping or tipping. Suitable for use indoor&outdoor, such as home, parties, travel, school, riding,and office time.