Batwing internal back panel to guard against water penetration through the zipper. SuperStretch Neoprene on arms, legs and side panels for unrestricted movement. Heat Shield internal thermo lining to trap additional hear. 4-way SuperStretch plus DURAFLEX Nylon Neoprene on selected panels for the perfect balance of durability and flexibility. Mono-Bond Waterproof seams, glued and blind stitched for extra strength and seal. YKK #10 Non-corrosive heavy duty bronze zipper slide. SealSkin - smooth chest panel to reduce wind chill and heat loss. X-Seals at wrists and ankles to keep out water and prevent heat loss.