Hot Fix Flat Backs can be easily ironed on to textile materials such as wool, cotton, linen, viscose, lycra, alcantara, silk, synthetics and denim, to name just a few. The flat back of the crystal has a layer of hot-melt adhesive that is activated by using heat and then bonds with the carrier material. They are wash-resistant. This is the new cut called the Cosmic Delta, #2720 by Swarovski, a beautifully faceted triangle.