Hi, thank you so much for your valuable feedback and sensitivity to technical details. In fact, Lycra (elastane), which provides flexibility, is already available in our product. Bamboo yarn, by its very nature, is incredibly soft and delicate. When woven alone, it frays quickly, loses its shape, and is prone to holes. Polyamide (nylon) is used as a technical necessity in 99% of high-quality sock productions worldwide to add durability and longevity to the product without disrupting the breathable natural structure of bamboo. Lycra and polyamide are located together in the framework of the sock. Since the main surface and the part that touches your skin of our product is made of bamboo in a high rate, you can use it with peace of mind without worrying about sweating or smelling. We wish you pleasant days.