Most automobiles and motorcycles use cast aluminum pistons that are made by pouring melted aluminum into a mold. In contrast, a forged piston is made by heating the aluminum alloy to below the melting point and forcing it into a mold under pressure (forging). Because the aluminum is not melted, there is less effect on the molecular structure and it retains the strength of the original aluminum alloy. And, because the resulting aluminum is stronger, the piston can be made thinner and lighter. That is what contributes to a reduction in inertial mass created by the reciprocating motion of the distance. For this reason, forged pistons have been used in luxury cars and race machines. In the YZF-R15 a forged piston is used to achieve a great revving feeling from the engine.