1 1/2" outside diameter 35mm inside diameter for Porsche 911. The same design as used on the 73 & 74 RSR cars. These are well made headers that will increase performance and last a long time. We have tried the headers available for less and they quickly fell apart. These headers are designed to work with custom made race mufflers or straight pipes. Header kits include all needed gaskets, nuts, bolts and washers.
