Dual-wall construction: Insulating layer of air keeps heat out and cold in * Inner foil liner reflects solar rays for added thermal protection * Constructed of low density polyethylene (LDPE #4): a durable, lightweight, and FDA food-grade approved material that complies with the Consumer Product Safety Improvement Act of 2008 (CPSIA) and California Proposition 76 * Reusable and durable; a practical and environmentally friendly alternative to disposable water bottles * 20 oz bottle includes a removable carrying strap so you can easily carry it or clip it to your gear