1-3/4" thick full flush (seamless optional) styles Available in 20, 18 and 16 gage steel face sheets. Galvanized steel also available. Available with 20 gage galvanized textured steel skins. "R" factor: 2.44 (Reference: 1" Thermal Pane Glass R = 2.0) "U" factor: 0.41 "STC" (sound transmission class): 32 Impact resistant, full honeycomb core is sanded-edge. Crush strength is 45 PSI. Hemmed, smooth finish edges. Seamless edges available. Inside coated with waterproof adhesive for secure bond and rust prevention. Hinge reinforcement 7 gage steel (3/16" plate). Chemically treated for paint adhesion. Oven-dried baked-on factory primer. Patented mechanical interlock eliminates weld marks, adds rigidity. Inverted top and bottom end channels welded to both face sheets for added stiffness. Optional steel or vinyl closing caps available. Easy to glaze with snap-in screwless aluminum glazing. Optional steel applied or flush welded glazing available.