As mentioned before, I’m not an engineer, but it’s good to know some basics about the materials you’re working with. There are generally two types of tubing recommended for use in cage design and we feel in most situations, only one is practical for use in a unibody car. The two materials are chromoly and DOM (drawn over mandrel) mild steel. We use the DOM material in our cage design. Why? Chromoly is the go to choice for a lot of cage builders because it’s stronger than DOM at the same tube size. Some sanctioning bodies allow for the use of smaller tubing with cages built from chromoly, thus a chance to save weight. Unfortunately, like most cool things in life, there are drawbacks. Chromoly is more brittle than DOM mild steel and when it fails, it can fold rather than bend. Also, it is more sensitive to heat, so where joints are welded, the chance of failure increases unless the joints are normalized. What is normalization? Normalization is where hardenable steel is heated above its upper critical temperature (north of 1300 degrees F in this case) and allowed to air cool to improve its ductility and toughness properties. Some builders just torch the joints and call it good, but doing it properly would actually call for baking the whole car. Not very realistic and the unibody probably wouldn’t handle it regardless. DOM cages don’t have these particular drawbacks.