These headers measure 1 3/4" O.D and 42MM I.D. and are recommended for 3.4 - 3.8 liter Motors. Our headers are made in the USA from equal length, mandrel bent 16 gauge mild steel. All headers maximize flow by utilizing 3 into 1 RSR collectors that are scallop cut. These headers are designed as a simple bolt on with no modifications needed. European Racing Headers also offers megaphones that bolt on to our headers. These extremely light weight systems are built for big horsepower with a broad torque band. Headers come with all gaskets, nuts, bolts and washers needed. Headers are sold in pairs only. We offer Ceramic Coating Services (See website)!