Jeff - DOM stands for "drawn-over-mandrel", and refers to the process used to manufacture the tubing. As James said, if you're going to be racing in IT then you really need to get the 2003 GCR (General Competition Rules) and read it. You can get an order form from the SCCA website. The GCR will tell you everything you need to know about the roll cage material, tubing size, and basic design requirements. It's the only way to make sure you'll be 100% legal. Oh, and did I mention you should also get a copy of the 2003 GCR?
------------------
Earl
ITA 240SX in process