Product description mr. Gasket stainless steel header bolts feature a washer-faced, smaller-than-standard hex head that's perfect for getting into tight spaces. Designed to withstand the abuse of red-hot exhaust ports and prevent leaks created by under-tightened header bolts, they're made of corrosion-resistant stainless steel, have 3/8 coarse threads, are compatible with chevys, chryslers, and pontiacs, and come in sets of 12.