Converter & pipe front bolt. A spring Bolt, which is a specially designed shouldered Bolt with matching spring and nut. It is designed to bottom out against the flange, which preserves the spring's force (acting as a locking measure) without over-compressing it, which can lead to failures during the high temperature cycles found in exhaust. These Bolts always mount through the flange, with a nut on the backside. An exhaust Bolt is a specialized fastener designed to secure various components of an exhaust system, including the manifold, catalytic converter, and exhaust Pipes. Catalytic Converter Bolt. Exhaust Manifold Bolt and Spring. Exhaust Muffler Bolt. Part cannot be reused/reinstalled. Part has related component that cannot be reused/reinstalled; gasket and nut. Included with: Converter & Pipe.