These BBK Performance shorty tuned Length exhaust Headers are designed and constructed as direct fit replacements for all 99-04 GM Truck and SUV 4.8L and 5.3L applications. Each header is manufactured with 1-5/8" CNC mandrel bent tubing that offers unrestricted exhaust flow for increased horsepower and torque over factory OEM manifolds. BBK tuned Length headers offer improved scavenging waves for better combustion, which leads to improved performance and fuel economy over stock or equal Length headers. As with all BBK Performance exhaust headers they feature a 3/8" laser cut flange for additional strength and a guaranteed leak free fit. All headers are robotically and precision hand welded and then pressure tested to ensure years of reliability and performance in the real world. All BBK exhaust headers are available in a Titanium Ceramic or polished silver ceramic coated finish and include new exhaust header gaskets, header bolts and hardware to complete the installation. IMPORTANT NOTE: On The passenger side OE Manifold you must remove the factory OE doughnut gasket and reinstall on the BBK passenger side header so the mid pipe will bolt up and seal