The Castelli Rosso Corsa 9 is just like the Rosso Corsa 13 and 6, but with a medium height 9cm cuff. Identical to the other versions, they are woven with Meryl Skinlife antibacterial fibers. The sock is thus wicking, will feel dry pretty much in just about every circumstance save a rainstorm. The top of the foot is a diaphanous web, ultra thin and extremely breathable. In the middle of the foot, the arch area, there is a high density band woven in. You won't notice any difference in thickness, but you will feel like the sock is becoming one with your foot rather than sliding around between your foot and your shoe. The toe has a flat seam for comfort and the cuff at the top is folded over to keep the sock from slipping. The Castelli Rosso Corsa 9 Sock comes in three colors: Black, Red, and White. The toes, heels, mid foot band, and cuff logos are in contrasting colors. Sizes are SM, LXL, and 2XL.