The right gear can make or break any expedition. That's why SmartWool created the new SmartWool Men's PhD Outdoor Mountaineer Socks, their most technical mountaineering socks ever. Putting some serious sock science to work in the PhD Outdoor Mountaineer, including revolutionary Indestructawool technology for ultimate durability and the 4 Degree elite fit system for a dialed fit. SmartWool 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. Benefits: PhD: Built for Performance in the Highest Degree 4 Degree%u0099 Elite Fit System: Uses two elastics for greater stretch and recovery to keep the sock in place Indestructawool: Indestructawool technology features a construction method for exceptional dur