Guhring 3 mm Extra Long HSCO Series: Guhring is a global leader in precision drilling. Their extra-long series (such as Series 502 or Series 671) provides the rigidity and heat resistance required for deep-hole applications. Some variants even include TiN coatings for added durability.
Oren HSCO Extra Long DIN 1869: Specifically designed for extra deep holes, these cobalt drills are built for industrial performance in hard metals.
Addison Extra Long Series: A reliable Indian brand for industrial tools. While their standard 3 mm bits are widely available, they also manufacture extra-long variants upon request or through specialized distributors.