GM LS Header Bolts M8 x 1.25mm, 1.181" (30mm) UHL - Black FinishWhen installing aftermarket exhaust headers you will need new header bolts, factory exhaust manifold bolts won't work as the flange could be thicker or the original bolts could be damaged. These Aeroflow header bolts are made from chrome moly 8740 material for high strength properties. They are coated in a black oxide for protection and long lasting durability. Each bolt features a compact 12 point head which is ideal for use where space is minimal