The Nano-Air Light Bottom uses Patagonia's innovative technology to keep us warm, mobile, and active as we play in the mountains with a design that feels like we're wearing nothing at all. Forty grams of FullRange insulation wards off cold conditions without restricting stretch or blocking breathability, and in classic Patagonia style, this bottom is made with recycled materials and protected with an eco-friendly PFC-free DWR finish.