The tag has been neatly removed. Only tried on indoors, so it's in beautiful condition. It has ventilation, so I think it can be used for mountain climbing, trail running, marathons, etc. From the official website: This cap is lightweight and can be carried compactly. The material uses stretch nylon ripstop fabric, which has a moderate firmness and provides a light and comfortable fit. The brim uses a material that is soft and doesn't easily crease when folded, allowing it to be packed compactly. Ventilation is provided at the front and back of the main body to reduce stuffiness inside the headwear. It's comfortable to wear and compact to store, making it a lightweight headwear that's useful for everything from long-distance hiking to mountain climbing. Fabric Ripstop Recycled Nylon Active Stretch (86% nylon, 14% polyurethane) Function Ventilation at the front and back of the main body / Piss name logo Country of origin: China Size F Color (IS) Indigo Stone Remarks Suitable size (head circumference): F (56.5～59.5cm) Brim length: 5.5cm