Connect threaded studs or rods with these internally threaded coupling nuts (AKA extension nuts). Coupling nuts have several applications. For example, they can piece together tie rods for longer reach, or they can serve a reducing function as a coupling nut reducer, joining two rods of differing diameters. These types of coupling nuts are usually constructed in a hex shape for wrench hold. Longer than the typical nut, these nuts vary by fastener thread direction, diameter, thread size, finish, length and other considerations. For more nuts, see our hex nuts, locknuts and acorn & cap nuts.