Gudgeon Pin
Also called the “piston pin” or “wrist pin”, it connects the
piston to the top of the con-rod by the little end bearing. On car engines this is the hardened alloy steel pin which connects the piston to the small end of the connecting rod. It allows the latter to pivot in the piston while transferring the force of the expanding gases on the piston to the rotating crankshaft. In order to reduce the reciprocating mass gudgeon pins are usually hollow.