The YWW 40 T system is designed specifically to meet the performance requirements of window walls for multi-story buildings. Glass is set to the front of the system to maximize thermal performance and is glazed from the interior of the building for labor savings. The YWW 40 T system is thermally broken by YKK AP’s patented MegaTherm® technology. The assembly sits down on a thermally broken sill flashing member. Head, horizontal, and sill members are secured to the two piece vertical members employing YKK AP’s patented screw spline assembly.