S/B Chevy flow pipe is 11″ length and 1.750″O.D.” Tig welded with gloss black finish. This has a dual bolt pattern which will fit both outer and center exhaust ports on General motors small block chevy Gen 1 standard 23 degree cylinder heads. By testing your exhaust port with and without a pipe you will know how it effects the flow positively or negatively. Flow pipe improves flow roughly 5 percent over an exhaust port with no pipe. Mounting hardware included.