Official MUTCD Compliant R1-1 STOP Signs. Heavy Gauge Rust Free .080 Aluminum STOP Signs. Diamond Grade Reflective sheeting (DG3) - offers optimized retroreflective performance to make signs more visible for every driver. DG3 uses unique technology to optimize performance in a changing driving environment. Increased observation angles and reflectivity are achieved. Diamond Grade Cubed provides higher luminance values at the most critical distance to drivers - 500 feet and closer. DG3 meets ASTM D Type IX specifications for reflectivity and features a reduced emissions and energy manufacturing process. DG3 STOP Signs feature twelve year reliability.