A seriously well-equipped military boot sock from Finl&, originally developed for The Netherlands Marine corps as training socks, Uphill Sport OPERATOR 4 Layer Comfort Bamboo & Merino Wool Socks are warm, heavyweight (110gm) technically advanced boot socks with protective cushioning to the front of the elasticated, ribbed crew length leg & half cushioning to the feet. The socks have elasticated arch bands for support & grip, & 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 & comfort, & for the soles, merino wool on both the outer & innermost layers. This makes the socks soft, breathable & great at transferring moisture to keep feet cosy & dry, even when you're exerting yourself on long marches.