An internal sleeve or nozzle is inserted into the exhaust pipe and when inflated, it expands and thus adapts to the inside of the exhaust pipe.
The sleeves are made for compressed air activation and the nozzles are activated with the attached hand pump.
The sleeves and nozzles are available in different sizes and can be used for many different car models with single exhaust pipes.
Some of the internal sleeves and nozzles have a Kevlar lining which reduces friction and resists higher gas temperature.