Ideal for use in lightweight walking boots and trail shoes the Smartwool PhD Outdoor Light Crew features Indestructowool™ Technology for improved durability and reduced fibre compression in high wear areas and Smartwool’s 4-Degree Elite Fit System, to keep the sock in place and giving you all-sport versatility. The PhD Outdoor Light Crew socks contain a high percentage of Pure Merino wool which offers excellent breathability along with odour control and you don’t have to be heading up a mountain, these are my socks of choice for long days in our Newcastle store.Smartwool PhD Outdoor Light Crew Features: 56% Merino Wool, 41% Nylon and 3% Elastane Light Cushioning Crew Height Indestructowool™ Technology 4 Degree™ Elite Fit System Mesh Ventilation Zones