Use the Snap-on’s 1/2" drive, 12-point 5/8" low-profile swivel impact socket, No. IPRD20, on starter bolts for most heavy duty engines. This socket offers a Flank Drive wrenching system allowing the socket to deliver 15 to 20 percent more turning power. This tool has a 30-degree uninterrupted swivel action for greater accessibility in tight quarters. Heat treated to a lower hardness. Recommended for starter bolts on Cummins, Caterpillar and International engines and Detroit Deisel series 60 starter bolts.