Double wall stainless steel construction. Inner wall is plated with copper for ultimate conductivity to keep drinks hot for 12 hours and cold for 48 hours. Wide mouth opening for easy cleaning and filling. The True Wireless Bluetooth Earbuds are the future of Bluetooth earbuds. As you see, there is no wire connecting the earbuds. The screw-on lid also doubles as a charging station IPX5 Water Resistant. Once the case is charged it can be used as a portable charger for your earbuds. The case is capable of charging the earbuds from 0 to 100% 2 hrs. With over 2 hours of talk time these earbuds are a must for any traveler. The ergonomic design of the earbuds keep them in place on the go. Bluetooth working range is 10 meters (33 feet). Playback time at max volume is 2 hrs generally. Stylish design with multiple functions makes this item the perfect gift.