Keep your hots hot, and your colds cold with Hydro Flask. Hydro Flasks are vacuum sealed bottles, and features double walled vacuum insulation, keeping hots hot for up to 12 hours, and colds cold for up to 24 hours. Find the perfect Hydro Flask for overnight camping trips or while on the trail. HeartRateMonitorsUSA.com has a variety of sizes and designs to choose from like the Hydro Flask 12 oz. BPA-Free Standard Mouth Insulated Stainless Steel Bottle (Everest Blue), Hydro Flask 18 oz. Narrow Mouth Insulated Stainless Steel Bottle (Green Zen), and More!