Some cars, such as Vauxhalls and Opels, use a different type of coil called an open coil. The unit is not contained in a round outer casing but is square.
If your car has an open coil, take care not to touch the coil when the engine is running or you may get an electric shock. If there is any danger of shocks from an open coil, there is usually a warning sticker on the bodywork.
If you find that your car has this type of coil, a new one may be difficult to find in a hurry. You can replace an open coil with a conventional coil, but check in your workshop manual or with your dealer to find out if you need a 12 volt coil or a special 9 volt ballast-resisted coil.
The low-tension and high-tension circuit connections are often the same as on a normal coil so the swap is quite easy. Disconnect the wires to the coil, then release the nuts and bolts, or screws, that secure the coil to the body. If you are fitting a normal coil you should be able to fit it easily.