Official MUTCD Compliant R1-1 STOP Signs. Heavy Gauge Rust Free .080 Aluminum STOP Signs. Engineer Grade Prismatic (EGP) - typically used in areas of low traffic volume, low speeds, and minimal competing light. Signs that commonly use Engineer Grade are Stop signs, parking signs and no trespassing signs. Engineer Grade meets ASTM D Type I specifications for reflectivity and features a solventless manufacturing process, reducing emissions and energy use. EGP STOP Signs can expect at least seven years of reliability.