The Hydro Flask 21 oz Standard Mouth can be stashed in easily into a small shoulder bag, side pocket, or a car cup holder. It holds enough to keep you going for hours. It is undoubtedly one of the bestselling vacuum insulated water bottles due to its size and versatility. It is insulated with TempShieldTM to eliminate condensation. It is made of durable 18/8 Pro-Grade stainless steel construction and is BPA-Free and Phthalate-Free.