For utility vehicles there are pistons consisting of one and two parts. The latter stem from the large engines. Large engines may reach diameters of half a meter and more and help to generate performances of more than 100.000 kW. The sense of splitting the piston in two parts lies in the different requirements for the material, on top it is steel and below special casting. Therefore, with utility vehicles the piston is assigned rather to the upper engine-power class. In this case the piston crown consists of steel and the piston shirt of light metal. Indeed, these pistons can stand higher ignition pressures, however, are mostly also heavier. Looking at the piston on top in the picture, you see a reduced-shaft bolt connecting both parts. To the right and left besides, the surrounding channel for the oil hose cooling is recognizable.