SmartWool PhD Run Ultra Light No Show Sock Patented ReliaWool technology in high impact areas provides superior durability Style: SW0SW147. 200 needle construction provides highest knit density while maintaining ultra light weight. Ultra Light Cushion: Minimal cushioning for maximum performance in close-fitting shoes. PhD = Built for Performance in the Highest Degree. Mesh Venting: Men&#39;s-specific mesh ventilation zones provide additional breathability and moisture management 4 Degree Elite Fit System: Uses two elastics for greater stretch and recovery to keep the sock in place. Lowest profile run sock available - Virtually seamless toe - Sock Height: Hidden