Frame - fabricated of 18-8 type 304 stainless steel with exposed surfaces having a #4 satin-finish. One piece roll formed angle is 5/8" x 5/8" (16 x 16mm) welded- frame. All welded construction. Corners are welded ground and polished smooth. Back Panel - fabricated of galvanized steel. Shock absorbing material is placed between mirror and back panel. Standard Mirror Glass - #1 quality, 1/4" (6mm) plate/float glass guaranteed against silver spoilage for 25 years. Meets and exceeds federal specifications DD-M-00411B & C. S. 27.