NATHAN One-Hand Hydration 300ml Flask Set In excellent condition with almost no damage. The inside of the flask has been cleaned. The flask has a self-sealing valve that allows you to drink with a single push without opening the cap. It is ultra-lightweight and compact, with a secure storage space with an easy-to-open zipper (size for a driver's license or credit card, approximately 2cm wide). Although the storage space is small, it is convenient for storing empty gel or energy bar wrappers during training. I am selling this as it has hardly been used since I bought it new.