Made of a high-quality 4340 steel alloy and heat treated to our exacting specifications, MPD Hollow Torsion Bars have won more Sprint Car championships than all other brands combined. Torsion bars feature 1-1/8" diameter x 48-spline ends, and may be ordered in diameters from 0.925" to 1.065", in both 29" and 30" lengths. Manufactured in the USA with all-American materials.