I measured the outside diameter. The only reason I was pretty confident in myself was because the outer diameter of my B and B was 2.5" and these pipes were 2.4" and I measured them both like five times to make sure I wasn't syching myself out. There's even a .1" ring on the sides of the pipes where they weren't quite as big as what they were on before. I'm 100% positive that the pipes I bought new from z1 are 2.4" so I guess it will confirm the diameter when I measure them tomorrow too. Like I said I wouldn't have even been a stickler had I not just bought brand new 2.4" z1 pipes. I even tried to help him out and sell his old pipes to a guy that he said was interested in them but he had already bought other pipes. I think the thing that pissed me off the most is that (if they are) 2.4" pipes, then it was a missunderstanding, but then it is ultimately a lie if he doesn't take them back and I don't like being lied to. At the same time I can understand the arguments for saying how some people could screw you over and send different pipes back b/c some people these days don't have any honor. As far as how I should have asked for pics with a tape measure placed to them when I bought them, I have seen how close most of you guys are on here so I assumed I could trust most of you and I still do but maybe I shouldn't have to this extent. I'm not trying to be a dick, I just expect what's right to be done.