The Chill-Its 6240 Phase Change Cooling Vest Extenders add 3.5in // 9cm of stretch to Chill-Its Phase Change Vests for an expanded size range and more customized fit across various body types. Made from 100% elastic with secure hook & loop attachment points, these extenders are designed for quick, easy installation. Compatible with Chill-Its 6215 and 6225 Premium FR Phase Change Cooling Vests as well as Chill-Its 6235 and 6230 Standard Phase Change Cooling Vests.