School Sign S4-3 8" x 24" 3M .080 3M Yellow w/Black copy Reflective on .080 aluminum, center mount holes. Used as a rider with other school signs. All School Signs are fabricated with sturdy .080 aluminum and your choice of Standard (new 3M Grade) High Intensity reflective or the new Florescent yellow/green Diamond Grade for maximum increased visibility-see prices below. Our signs are manufactured to meet strict MUTCD requirements, and our heavy gauge (.080 mil) rust-free aluminum reflective signs are guaranteed for at least 7 years of service.