Aftermarket exhaust systems are modifications made to a vehicle's exhaust system after it has been purchased. These systems are designed to improve performance, enhance sound, and reduce weight compared to factory-installed exhausts. They can include components like mufflers, headers, and catalytic converters that are engineered for better airflow. Many car enthusiasts choose aftermarket exhaust systems to achieve a more aggressive sound or to increase horsepower. These systems can also be made from various materials, such as stainless steel or aluminum, which can affect durability and weight. Overall, aftermarket exhaust systems offer customization options for vehicle owners.