TechKewl Phase Change Cooling Vest w/ Hydration System Includes: Set of four 6665 Cool Pax & Hydration Reservoir6627 TechKewl Phase Change Cooling Vests w/Built-In Hydration System: All the attributes of the 6626 plus Built-in hydration pocket and drinking hose w/valve; V-neck w/zipper closure, and hook & loop girth adjustments 70 fl. oz. (2 liter) bladder; 100% cotton (excluding inserts) Include one (1) set of Cool PaxTM Phase Change Cooling Inserts (6665) Includes Hydration System (6660) Includes Cooler Bag TechNiche's Phase Change Cooling Vests maintain a comfortable 14 degrees C (58 degrees F) for up to 3 hours of critical heat stress relief.They are commonly used under high heat protective clothing, hazardous material suits, military body armor, and mascot costumes. TechKewl™ Phase Change Cooling Vests keep you cool when you need it most! Avoid Heat Stress Stay Safe Great for Working Outdoors Works in extreme conditions Regulate Body Temperature TechKewl™ Phase Change Cooling Vests are specially designed for long lasting durability in harsh working conditions. Vests have a comfortable v-neck design with a zipper closure. Hook and loop girth and shoulder adjustments provide a customized fit. V-neck w/zipper closure; hook & loop girth adjustments 100% cotton (excluding inserts) Thermal Liner Includes front chest pocket Include 1 set of 4 (Four) Cool Pax™ 7065-V Phase Change Cooling Inserts How Phase Change Cooling Works: 1) Freeze Cool Pax™ Ice Inserts (Included) 2 )Place in vest for hour of cooling 3) Frozen inserts provide extreme cooling effect Key Benefits of TechKewl™ Phase Change Cooling: Provide cooling comfort and heat stress protection in high temperature environments. Commonly used in extreme heat under work gear, costumes, and other apparel. Phase Change Material releases long-lasting, temperature-specific (58 degrees F, 14 degrees C), cooling relief. Non-toxic, non-flammable, durable, reusable, lighter than water, and does not produce condensation. TechKewl™ Activation & Use: Simply place in a freezer until solid. Or submerge inserts in ice water for up to 45 minutes. Place inserts to garment pockets. Wear comfortably; repeat steps as needed (or use additional inserts for continuous relief). TechKewl Phase Change Cooling Vest with Hydration System