This is the 4th Element Arctic Socks Drysuit Undergarment Thermal Protection Features: Keep Feet a Bit Warmer & Comfortable in Neoprene Boots Dry Suit Sock with Water Resistant Outer Layer Arctic Socks, Completes the Thermal Protection System Low Bulk Thermal Protection to Extremities Two Layer Construction Warm and Comfortable Inner Liner Can Be Pulled Out from Outer Liner to Speed Drying Times Outstanding Performance of Xerotherm with Additional Thermal Layering Next Stage Development of High Performance System Fast Wicking, High Insulation Fabrics Arctic Creates Micro Climate Around the Wearer Keeps Body Dry and Warm High Density Inner Fleece Provides Superior Insulation Suitable for Year-Round Use Underneath Dry Suits Continue to Perform when Wet All Seams are Flat Stitched for Added Comfort The Arctic drysuit undersuit is complemented by the Arctic socks, which completes the thermal protection system, offering low bulk thermal protection to the extremities. The two layer construction is warm and comfortable, and the inner liner can be pulled out from the outer liner to speed drying times.