The Castelli Free 9 Sock is woven with Meryl Skinlife antibacterial fibers. This moisture-wicking, breathable fabric pulls sweat away form your skin to keep you dry and comfortable. 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. Castelli also added an open mesh panel to the cuff to allow air to move freely through the sock.
The Castelli Free 9 Sock comes in three colors: Mandarin, Ocean, Red, and White. Sizes are S/M, L/XL, and 2XL.