Im looking at the possibility of purchasing a Autopower 'Race' rollbar. However, the seller does not know whether the tubing is of ERW or DOM peices.
So my question is, what are some clues to distinguish the two by the naked eye?
TIA.

 

Look down the inside of the tube, and ERW will have a visible seam. It should be pretty easy to determine.

 

Tech inspectors do not have the time to look inside the tubing-even if that is a way to determine the type. IF you want to be really safe with this purchase-you need to get a bar/cage that has a certificate from the builder that states in writing what material it is made from. I carry one in my logbook. KIRK Racing gives you one and it states DOM and the other specs for the tubing. I would think that AutoPower would be able to do this for you too. Remember that it is your responsibility to have the proofs. If this seller cannot provide the documentation-pass on it.