CW-X Women&#39;s Insulator Running Long Sleeved Zip-T,Black,Medium Long sleeve zip-T using 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 Used as warm functional primary layer or outer layer depending on weather conditions Medium weight with comfortable stretch qualities