Railroad car coupler assembly knuckle pin

A railroad car coupler assembly knuckle pin comprising:

• an elongated cylindrical tubular body having an upper end portion, a lower end portion spaced apart from the upper end portion, and an intermediate portion between and connecting the upper end portion and the lower end portion, the body including an elongated cylindrical wall having an outer surface and an inner surface that defines an elongated central opening that extends the length of the wall, the elongated cylindrical wall including two spaced apart elongated opposing surfaces that define an elongated slot that extends the length of the wall;
• an annular first ring integrally connected to and outwardly extending from a first area of the upper end portion of the body;
• and
• an annular second ring integrally connected to and outwardly extending from a second area of the upper end portion of the body, the second ring is spaced apart from the first ring along the body;
• wherein the first ring defines a plurality of first stress relief slots, the first ring including four equally sized sections, each section including a curved wall having a top surface, a bottom surface, a concave inner surface integrally connected to the outer surface of the wall of the body, a convex outer surface, a first end surface that partially defines one of the plurality of first stress relief slots, and a second end surface that partially defines another one of the plurality of first stress relief slots.