This great phase change vest has proven its effectiveness in preventing heat stress. Simply freeze the reusable phase change cooling inserts and experience hours of reliable cooling relief in any condition. Phase change material releases temperature-specific 58\xC1F cooling relief to protect workers in high heat environments. One Size Cools for 2-3 hours, set at 65\xC1 Wight 6.5lbs. Adjustable mid section & shoulders Includes Phase Change Cooling Pack Item # PC-CPK Great for: Construction, Landscaping, Road Work, Welding, General Warm Weather Work, Warm Weather Outdoor RecreationMiracool Phase Change Cooling Pack Item # PC-CPK: Cools up to 4 hours, set at 65 degrees Additional spare cooling packs for PC-VV & PC-VVFR Non-toxic Packaged in snap handle bag Made in the USA About Phase Change Materiel: Commonly used under military combat gear, hazardous materials suits, mascot costumes, and other apparel. Provide cooling comfort and heat stress protection in high temperature environments. Phase Change Material (PCM) releases long-lasting, temperature-specific 58F (14 degrees C), cooling relief. Phase Change Material (PCM) is 30% lighter than water. PCM is non-toxic, non-flammable, durable, reusable, lighter than water, and does not produce condensation. Benefits of Phase Change Cooling Vests: Heat Stress Protection Helps prevent exhaustion and dehydration Provides cooling comfort in high temperature environments Reliable and Reusable Trusted by US Military and Armed Forces Phase Change Vs. Evaporative Cooling: Phase change cooling provides a lower cooling temperature as compared to evaporative cooling products. The main difference is that evaporative cooling products are activated in water and use the evaporation process to provide cooling, and phase change products utilize freezable charge packs to provide the cooling effect. Phase change products typically get colder than evaporative items but do require re-freezing or extra charge packs for extended use. MiraCool Value Nylon Cooling Vest with Phase Change Inserts