It is a rod piece used to connect the drilling bit and transmit power.

Drill rod is a seamless steel tubular product used to transmit rotational power and drilling fluid from the surface to the drill bit while providing the mechanical strength necessary to apply weight on bit. Manufactured in compliance with API Spec 5DP, drill rods feature tool joints at both ends-pin and box connections-that enable rapid make-up and break-out during tripping operations. The tube body is manufactured from high-strength alloy steel with controlled mechanical properties to withstand the complex combination of tension, compression, torsion, and internal pressure encountered during drilling. Available in various steel grades, diameters, and wall thicknesses, drill rods are selected based on well depth, hole size, and anticipated loading conditions.