RPC Exhaust Header Reducers are a must when updating your exhaust system or just simply adding or replacing a set of headers. These header reducers are made from heavy gauge aluminized tubing and designed for headers with a 3-bolt triangular flange. RPC Collector Gaskets will keep all exhaust gases flowing through your headers, not around the flange, for a leak proof seal. Each header collector gasket is made of the same copper high-temperature material. These gaskets are 0.0400" thicknesses.