The GM GENUINE 12671388 & 12671387 NOX Sensors are specifically designed for a 6.6L Duramax engine, with both upstream and downstream sensors included. These bolt-on sensors come with a wire harness for easy installation and feature blade and bullet terminals for a secure connection. Made of metal and with a black connector color, these GM OEM sensors are a genuine replacement part with OE/OEM part numbers 12671388 and 12671387. Perfect for front placement on the vehicle, these sensors offer easy installation and are not vintage parts or universal fitment.