The 100% Merino wool interior provides excellent moisture control and comfort while the nylon exterior provides maximum durability and abrasion resistance. Other critical features include: Berry Compliant. Fully cushioned foot and leg. Merino wool next to skin feels great and is naturally anti-microbial and flame resistant. Nylon reinforcement on the outside of the sock for increased durability. Heel Lock ® provides heel security that limits the chances of a blister when combined with a properly fit boot. Dynamic Toe Cup ® limits the amount of material in toe box to prevent bunching in a critical area of the foot. Knitted construction naturally moves the seam back from the sensitive toe area.