Frame - 430 Bright anneal stainless steel, One piece roll formed angle is 1/2" x 1/2" x 1/2" (13 x 13 x 13mm). Mitered corners. Back Panel - fabricated of galvanized steel with tab lock and slots formed to receive wall hanger tabs. 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 15 years. Meets and exceeds federal specifications DD-M-00411B & C. S. 27.