A. Seamless or DOM mild steel tubing (SAE 1020 or 1025 recommended) or alloy steel tubing (SAE 4130 or T45), or Docol R8 tubing must be used for all roll cage structures. Alloy and mild steel tubing may not be mixed. ERW tubing is not allowed.

B. The following table shows the minimum allowed tubing outer diameter and wall thickness by vehicle weight:

Vehicle Weight (not including driver)	Tubing Size (inches) (outer diameter x wall thickness)
Up to 1,000 lbs.	1.00 x 0.060
1,001– Up to 1,500 lbs.	1.25 x 0.090
1,501–1,700 lbs.	1.375 x 0.080
1,701–2,699 lbs.	1.500 x 0.095 1.625 x 0.080
2,700 lbs. and up	1.500 x 0.120 1.750 x 0.095 2.000 x 0.080

C. For purposes of determining tubing sizes, the vehicle weight is as raced without driver, fuel and ballast. The minus tolerance for wall thickness should not be less than 0.010 inch below the nominal thickness.

D. The required tubing elements must meet the material minimums set forth above. Optional tubing elements may be any size.

E. The minus variance of tubing wall thickness due to manufacturing tolerances is limited to 0.010 inch.

F. Either an inspection hole between 3/16- and 1/4-inch diameter must be drilled in a non-critical area of the front and rear hoops, as well as one of the supplemental braces to facilitate verification of wall thickness; or alternatively, wall thickness may be determined by non-invasive means and noted in the logbook and inspected by such means.