SealSkin Waterproof and Breathable Socks MED SEAL SKINZ RECOMMENDS WIGWAM COOLMAX SOCK AS A LINER, OUR ITEM 6162 OUTSIDE LAYER: NYLON & SPANDEX MIDDLE LAYER: WATERPROOF MVT (MOISTURE VAPORT TRANSPIRATION; ALLOWS PERSPIRATION TO ESCAPE WHILE NOT ALLOWING WATER TO PENETRATE. INSIDE LAYER: DUPONTS COOLMAX YARN THIS COMBINATION PROVIDES A SOFT, FLEXIBLE,STRETCH-TO-FIT SOCK SUITABLE FOR A WHOLE LOT OF USES. THE SEAMLESS DESIGN PROVIDES THE ULTIMATE IN ACTION PERFORMANCE AND COMFORT.