Automotive studs are a headless bolt that is threaded at both ends with the center portion remaining unthreaded. They are used to insert one end into the head or block and then insert a nut or washer on the other end for applications such as bolting the exhaust manifold to the head. This Class 5.8 Metric Automotive Studs Assortment contains variants ranging from M6-1.00 to M12-1.25 in coarse & fine thread sizes. Full assortment contains fifteen (15) refills comprised of Hillman item numbers #4466 - #4480.