3120782 Worm-Circle Fits Caterpillar 9D1142 120G 120H 120H ES 120H NA 12G 12HOne New Aftermarket Replacement Worm Circle Drive Gear Fits Caterpillar (Fits CAT) Motor Graders This aftermarket replacement worm circle drive gear (also cataloged as a gear worm) is a key component of the circle drive system on Fits Caterpillar motor graders. The worm gear meshes with the internal ring gear of the circle assembly, allowing the operator to rotate the moldboard and adjust blade angle during grading operations. This is a wear component