The stock exhausts are the first thing motorcyclists consider changing in order to improve the performance of their motorcycles. Aftermarket motorcycle exhausts are also installed to improve the appearance or change the sound of motorcycles. Different motorcycles have different exhaust systems depending on the type of engine or model. Large four-cylinder motorcycles, for example, typically come with a twin exhaust system. Customizing the exhaust system of a sport bike often involves installing a slip-on muffler. Owners of cruiser motorcycles tend to replace the entire exhaust system. Leatherup.com has a large selection of aftermarket motorcycle exhausts, slip-on mufflers, and motorcycle parts.