This Ergodyne Safety Vest makes working under grueling hot conditions much easier and comfortable by ensuring that workers stay cool. The vest keeps workers cooler, safer and more productive and reduces risks of heat-related injuries. Durable cotton fabric carrier is treated with top-quality Banox FR3 for flame-resistant properties. Hook-and-loop closures quickly adjust at the shoulders, and around the body for a comfortable, exact fit. Anatomical over-the-shoulder design conforms to the body for improved comfort. Weighs less than comparable products - no batteries, blowers, heavy ice or gel packs. Fabric carrier is washable in mild soap; line dry. Two charge packs included with each vest. Charge pack instructions:place in freezer or refrigerator for 1hr-20min or place in a cooler of ice for about 20 minutes when fully charged the gel will be a solid white. Lasts an average of 4hrs the gel will turn clear when it needs reactivated.