[EarlsflyinCobra]

Hi Roger......The .120 or .134 is the wall thickness....most racing applications require the .134.
The 1 1/2 or 1 3/4 is the diameter of the pipe.....again I think most racing apps are 1 3/4 diameter.

I'm getting ready to order some dies for my friends mandrel bender. We had planned on ordering the 1 1/2 but may order the 1 3/4...maybe both....>Thanks, Earl