Abstract: Wrist pin for a two-piece piston, having a cylindrical external surface (41) and an internal surface with an internal diameter, throughout the length of the pin (40). The end portions of the pin have a reduced internal wall thickness between the outer half of the supporting face of the bosses (50), where there exclusively occur bending moment and shearing force applied by the inertia of the skirt (20) and of the moving assembly (100). The reduction in the internal wall thickness is obtained by the increase in the internal diameter of the pin (40) at the end portions, through two different end revolution surfaces (43, 44) each having respective a generatrix which is at least substantially straight.