Flywheels clamp onto an operating engine to transfer power to the wheels via the transmission system of a vehicle. You can find cheap replacement flywheels for your vehicle by searching by its make and model here.
In a vehicle in use, the flywheel is the round component that connects to the engine and rotates to maintain a constant flow of power to the wheels so that the vehicle can move. It disengages from the engine when the clutch is pressed so that the driver can navigate through the gears of the transmission system - this is impossible when the flywheel is connected to the engine. A vehicle cannot operate properly without a fully functional flywheel, so it is vitally important that its condition is managed and regularly checked. As one of the most significant parts of a car or van, it is important to have quality parts in place.