The J.B. Field's "30 Below XLR" sock is ideal for those who spend a lot of time outside in cold weather and is perfect for winter sports. With a full, heavyweight cushion and soft merino wool, they are sure to keep your feet warm and comfortable in the most extreme conditions—as low as -30ºC! The only differences between these socks and the "30 Below Classic" are the double cuff to help socks stay up better and both ankle and arch support, which prevents slippage and bunching.