Segments are an important machine element used in cars and airplanes and mostly made of steel alloy. The segment looks like a ring with a gap on one side. In English, it is denoted as a piston ring. The rings have excess space at the piston head to prevent the piston from expanding and jamming due to the high temperature generated. For this reason, the rings attached to the piston head play very important roles in the formation of the four strokes.

The rings at the head of the piston form the times by applying a certain pressure to the cylinder walls. Example: While the piston descends from the top dead center to the bottom dead center during the intake stroke, it prevents the air from the crankcase side to pass to the combustion chamber side, ensures a good vacuum is created in the cylinder and the mixture is filled into the cylinder at the intake stroke.