This is a pouch that attaches to the shoulder strap of a backpack. It can hold a flask or a 500mL bottle and is useful for mountain climbing and outdoor activities. I've used it a few times on low mountains. The whistle is unused. In the third photo, the rubber that secures it to the shoulder strap is loose (top only). 【Storage Capacity and Functionality】 It's compact but can securely store necessary small items and has an easy-to-organize design. It also has a whistle, which is useful in emergencies. 【Durability and Lightweight】 It uses lightweight and durable nylon material, making it easy to carry and long-lasting. ⚫︎ Brand: MILLET