The right gear can make or break any expedition. That's why we've created the new PhD Outdoor Mountaineer socks, our most technical mountaineering socks ever. We put some serious sock science to work in these all-mountain socks, including revolutionary Indestructawool technology for ultimate durability and the 4 Degree elite fit system for a dialed fit. We placed high-density cushioning where you need it most, in the heel and toe, while using a flat knit on the leg to accommodate low-volume mountaineering boots. Mesh zones offer breathability, flex zones offer added comfort, and Merino helps keep feet warm, dry and comfortable.