Size M, equivalent to 25cm-28cm. I bought a lot of these, but they haven't worn out, so I have some left over. They are currently sold out. The following is taken from the TF website: TF's best-selling, classic original socks. While preferences vary, these socks offer an addictive, outstanding fit and durability, providing the best balance and integration with your shoes. The material is based on cotton with anti-odor function (partially) and mixed with 10% synthetic fibers such as polyester to improve durability. The ribbing has 3 convex ribs and 1 concave rib. The ribbing, called "San-ichi," is made slightly wider to reduce constriction and create socks that don't cause stress. The part that touches the sole of the foot is half-pile (terry cloth from the toes to the heel) to provide absorbency and cushioning, reducing fatigue. These socks aim to have a certain amount of thickness while not being too thick, and to be durable, comfortable to wear, and functional. With that goal in mind, we repeatedly washed them to check durability, adjusted the tension of the elastic, and went through numerous trials and errors. We pursued both "appearance" and "comfort," remaking samples many times and even getting complaints from the factory, but finally, we completed these socks.