With the Hydro Flask Standard Mouth Flex Cap, you can add to your Hydro Flask's functionality. Made with recycled plastic and stainless steel pivots, this flex cap is extremely durable and is easy to carry. With the Honeycomb InsulationTM, your drinks will stay cold or hot for several hours. Pair the Hydro Flask Flex Cap with any standard mouth Hydro Flask water bottles for a durable way to take your favorite drinks to go. Features: BPA-free and phthalate-free Honeycomb InsulationTM keeps drinks cold or hot Compatible with all Hydro Flask standard mouth bottles Durable stainless steel pivots allow the strap to easily move