3.5mm nylon II neoprene utilizes glue and blind stitched seams for a superior water seal. New design provides a contoured and snug fit, creating a more comfortable and warmer boot. ZIPPER: YKK #5 self-locking and corrosion resistant zippers. Full-length zipper pocket minimizes water entry. A longer pull-tab on the heel allows you to don the boot with greater ease.