First decision is 110 or 220. 110 will limit you and is not something I would want to use on chassis tubing. While I'm old school and struggle through with an old Airco square wave transformer unit, I have used inverter units on steels and aluminum and they are fine. Miller does the Diversion and Lincoln does the Squarewave 200. Or if you have the budget, look at better units. I would prefer a good used higher end machine than a new imported toy. You get what you pay for.