Coupling nuts are long hex nuts chamfered (beveled) at each end and used to couple two externally threaded objects of the same size and thread pitch. They can join different parts, like a hanger bolt and a threaded rod, or connect identical items, such as two threaded rods, to extend length. Sometimes coupling nuts function as spacers/standoffs. They are also known as: extension nuts, rod coupling nuts, hex spacers.
Metric Coupling Nuts connect any two threaded items like two pieces of threaded rod. They have coarse right-hand machine screw threads at both ends. Length is dependent upon size, which is about 3 times the size of the nut. Choose from zinc plated steel and stainless steel. They are also known as Extension Nuts and Hex Spacers.