Produce Hexagonal and round cross sections, Hexagon rods are more rigid, heavier and transfer energy more efficiently, while increasing flushing. Round rods are generally lighter than hexagonal rods and are normally used in extension drilling applications. With the longer steel tending to be larger in diameter, conventional extension steel is characterized by a duplicate thread on each end of the steel. Extension rod size: T38(R38)-H32-R32 Extension rod, L3100mm; T38(R38)-H32-R32 Extension rod,L3700mm; T38(R38)-H32-R32 Extension rod,L4915mm.