Koch Industries 4021581 PTO Locking Pin with Square Wire Retainer, 5/16 x 3-1/2-Inch, Yellow Zinc Plated, 2-Piece Square wire retainer Diameter 5/16-Inch Useable length 3-1/2-Inch Used in farm, lawn and garden, trailer hitch receivers, and other applications to secure attachments and PTO accessories Pins comes in poly bag