SBM 273 318 340 360 Header Stud Kit Bolts Stainless Steel Small Block 5/16 Bolt Kit for Installing Headers to Cylinder Heads Hardened 304 Stainless Steel (12) 5/16" x 1 1/2" Studs (polished) + (12) 5/16" Hex Locking Flange Nuts (polished) SBM 273 318 340 360 Header Stud Kit Bolts Stainless Steel Small Block 5/16 Cuda Barracuda Dart - Bolt Kit for Installing Headers to Cylinder Heads - Fitment: Fits 273, 318, 340, 360 SBM Engines; Fits Most Short & Long Tube Headers; Will Not Fit: OE Exhaust Manifolds. - Specifications: Hardened 304 Stainless Steel; (12) 5/16" x 1 1/2" Studs (polished); (12) 5/16" Hex Locking Flange Nuts (polished).