ColdPruf Extreme Performance Expedition Weight Underwear Zip Mock Shirt - Women's Inside and outside layers are 96% CTF performance polyester, 4% spandex. Two-layer fabric construction helps provide a natural barrier of warmth. Coldpruf Technical Fiber (CTF) fabric delivers superior wicking and moisture management to keep you dry and comfortable. CTF contains Alpha Scan antimicrobial to keep the garment essentially odor free. 4% spandex provides comfortable close-to-body fit.