IIT 16736 Safety PTO Pin Assortment, 5-Piece 3" x 1/4", 3" x 5/16", 3" x 3/8" square pins 3" x 1/4" and 3" x 5/16" semicircle pins made of tempered carbon steel with zinc plating to resist rust Great for a wide variety of lawn, garden, and farm applications. Used to safely and securely attach trailer assemblies, hitches and couplers, these pins are small but important