Hi there, thank you for the question. Most US manufacturers knit socks to fit a range of sizes. At Boardroom Socks, we do this by using 30% stretch nylon so that they are able to adapt to a range of sizes in both the foot and the leg. Without this stretch nylon, the socks would essentially have to be sized and they would be significantly more expensive. The stretch nylon eliminates this and also makes the socks more durable. Let us know if you have other questions.