Measure the outside of the tube with a caliper guage. He wants to know if they are 1 5/8" or 1 3/4" and do you have 2 1/2" or 3" exhaust. maybe a part #?
lol dont hav a caliper gauge and no part number they were on the engine wen i purchased it he said hedman but i dont c the hedman stamp cuz i hav a pair