These midpipes are a direct replacement for your OEM mid-pipes and bolt up between your headers and cat-back system for a quick and easy installation. H-pipes maintain back pressure to give you more torque gains earlier in the RPM range for quicker launches. These h pipes are usually better at producing a constant growl for a uniform sound. X-pipes are designs to cross exhaust streams for a slight power increase over h-pipes. They are usually raspier and louder than other midpipes and produce more power in the higher RPM range. Catalytic mid-pipes feature high flow catalytic converters to give your more power over stock while retaining proper emission regulations to properly pass state inspections. Off-road mid-pipes do not have catalytic converters installed making them louder and they tend to make more power. These cat-less h-pipes and x pipes are designed for off-road use only and will require MIL eliminators to turn off check engine lights. Got a new 2015 Mustang and looking to turn up the sound? No problem! The new S550 Mustang actually refers to their midpipe as a resonator delete. The new Mustangs have this big, bulky resonator after the catalytic converters to help quiet things down. Adding a 2015 Mustang resonator delete will not only enhance sound, but it will also reduce weight! Look no further than Late Model Restoration for all of your Mustang mid-pipe needs!