It is not possible to cast clean and through holes in the metal body of a die cast model car. There must be some metal flashes around the hole opening during casting and need to be trimmed by hand using a cutter or a file. A die cast model car has many holes, large or small, as seen in this scale 1/18 Lamborghini Sesto Elemento's rear engine cover, they all need to be trimmed one by one. It is a very labor intensive process. The more holes the model car have, the more expensive it is to manufacture. Only plastic injection body can have perfect clean holes without the need of trimming.