This is CamelBak's "Marathoner Vest." It is a hydration vest for replenishing fluids during sports such as running and marathons. This product is from a specialized manufacturer of hydration equipment headquartered in California, USA. It has a system where a hydration bag is stored on the back, and fluids can be replenished through a tube. It features a lightweight design that fits the body and was developed for runners (quoted). After purchase, I did not have an opportunity to use it and kept it at home. I am listing it for sale as I am decluttering. It may be folded compactly for shipping. Thank you for your understanding. I will ship via either YuYu Mercari便 or RakuRaku Mercari便.