M24-3.0 x 72mm DIN 6334 Long Hex Coupling Nut

A coupling nut also known as extension nut is a threaded fastener for joining two male threads, most commonly threaded rod. The outside of the fastener is usually a hex so a wrench can hold it.
Coupling nuts are used in joining threaded rods where span of application exceeds 144" or where a threaded fitting is used with threaded rod in suspension applications. ISO 898-2 Class 6.6H thread requirement. Zinc plating, retards the corrosion rate in a normal atmosphere.