CW-X Women's Insulator Zip Running Vest Polyester 80% / Spandex 20% Imported Auto Sensor fabric moves perspiration away from skin and regulates next-to-skin temperature Silver dioxide fiber makes fabric antibacterial. 4-way stretch for comfort used for high performance support under layer or on warmer days use as outer layer. Flat seam construction for comfort Zip collar with wind flap and locking zip