We recommend use BBK Long tube Part #1533BBK Performance short mid X pipes are specifically designed to be used with BBK full length headers for 1996-04 Mustang 4.6L to complete installation to your cat back exhaust system. These BBK X-pipes are made from 2.5″ Tubing and feature a unique die stamped performance Xtracter center X section to ensure maximum flow and horsepower. Each BBK mid X pipe offers performance, quality and value that guarantees years of top performance for your Ford Mustang. Please note: ***NOT LEGAL FOR USE IN CALIFORNIA***BBK or Any of its Distributors – CANNOT SELL THIS PART TO ANY END USER WITHIN CALIFORNIA. THIS PART CANNOT BE SOLD OR INSTALLED ON ANY POLLUTION CONTROLLED VEHICLES IN CALIFORNIA. OFF ROAD pipes do not have any catalytic converters and are manufactured and represented ONLY for the purpose of OFF ROAD-RACE USE ONLY.BBK Short X pipes are for use with BBK Full Length Headers only.