Our most loved NANDEX ™ fabric (made famous by our 'Best Black Tights' or 'leggings' for our international customers), now available in Iris. STAX. NANDEX ™ is the perfect combination of a buttery smooth, high-performance fabric that can support you through your work out and your everyday, stylish lifestyle. STAX. V1 Cropped Tank sits cropped on the torso with a scooped neckline.