These Adapter Pipes are a great start when trying to connect Hooker Blackheart LS/LT Exhaust Manifolds to a catalytic converter and Hooker Blackheart exhaust system. The BH14351 best fits 4WD GM C1500 "OBS" projects that are planning on running a set of Hooker Blackheart LS or LT swap exhaust manifolds (8502HKR, BHS518, etc.) and need a great adapter piece to accomplish two things: 1) fill the gap between the end of the manifold and 2.50-inch inlet exhaust systems and 2) easily incorporate a catalytic converter. These kits were designed for compatibility with Hooker Blackheart engine mounting brackets listed for this vehicle application only. They are designed to provide the user with a means of installing the factory catalytic converters from a 1999-2006 5.3 or 6.0-liter Chevy Silverado truck (4.00-inch maximum diameter), into this vehicle application, within the stipulations/requirements published by CARB/EPA for emissions-legal engine changes. The ability of the final fabricated assembly to satisfy these requirements should be confirmed with local/state authorities prior to the installation of these components.