Thread drill rod other names extension rod, Extension drill steel, Extension drill rod, and Extension steel, M/F rod ( Speedrod ) , 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.

Drill rod using thread system. Drilling precision can be further improved by using this as the first rod in a normal drill string. Furthermore, since this is a speed rod design it will produce straighter holes and at least 10% higher penetration rate in good rock conditions compared to rod and coupling sleeve combination system.