Steel with a Zinc-Yellow finish Fine Thread 5/16"-24 thread Grade 8 Grade 8 steel hex head cap screws, 5/16"-24, 1.25" length, zinc-yellow coating. Made in North America. These hex head cap screws are made in North America. The six ticks on the head of our screws signifies that they are Grade 8, offering greater strength and durability than traditional Grade 5 cap screws. The zinc-yellow chromate coating offers a high level of corrosion resistance and rust protection.