A seriously well-equipped military boot sock from Finland, originally developed for The Netherlands Marine corps as training socks, UphillSport OPERATOR 4 Layer Comfort Bamboo and Merino Wool Socks are warm, heavyweight (110gm) technically advanced boot socks with protective cushioning to the front of the elasticated, ribbed crew length leg and half cushioning to the feet. The socks have elasticated arch bands for support and grip, and smooth toe seams for protection against blisters. These thermal grade 3 socks have a 4-layer Drytech structure with silver ion-enhanced polypropylene next to the skin, a layer of bamboo for moisture absorption and comfort, and for the soles, merino wool on both the outer and innermost layers. This makes the socks soft, breathable and great at transferring moisture to keep feet cosy and dry, even when you\'re exerting yourself on long marches.