Cobalt Kinetics CK-Pro 5.56x45mm NATO 13.7in Complete Upper Receiver Black Cerakote. All CK-Pro URGs are expertly built by our gunsmith staff. Built URGs are test-fired for function before leaving out the door to the customer. Upgrade your current platform RUN COBALT Specifications for Cobalt Kinetics CK-Pro 5.56x45mm NATO 13.7in Complete Upper Receiver: Manufacturer: Cobalt Kinetics Caliber: 5.56x45mm NATO Barrel Length: 13.7 in Finish: Cerakote Color: Black Package Contents: Cobalt Kinetics CK-Pro 5.56x45mm NATO 13.7in Complete Upper Receiver Cobalt Kinetics CK-Pro Urg 5.56x45mm NATO 13.70" Black Cerakote Receiver CKPROURG556137BLK