Silicone elastic. 3 large assorted boxes. White and black 0.5 mm thick, 8mm wide, for edging. White 0.5mm thick, 19mm wide, for waistbands/cuffs. I had to buy this in a bulk order as it is difficult to get in smaller quantities. I paid £50 per box, and had far more than I needed. It can be used for any garments but is also suitable for swimwear. There's loads of it left in the boxes.