Offered for those purchasing a BluePrint Engine Equipped with Holley Terminator X, that are also pairing a 4L60E or 4L80E to their engine. The Terminator X Max used on BluePrint engines can support trans control but requires this harness to mate the trans to the ECU harness. (BluePrint Engines Builders series engine/trans combos include this harness. Standalone Engine customers must purchase separately)