A pipe coupling features what characteristic?

A pipe coupling is designed to connect two pieces of pipe together, and it usually features inside threads on both ends. This threaded design allows for secure connections between pipes, making the coupling ideal for joining sections of piping in various systems. The presence of inside threads on both ends facilitates the easy attachment of pipe sections, ensuring that they are tightly secured yet removable if necessary.

In contrast, options noting outside threads on both ends or inside threads on just one end do not accurately describe pipe couplings, as these configurations would not provide the necessary functionality to connect two similar pipe fittings. Additionally, couplings can include certain designs that are completely smooth, meaning they have no threads at all, but this is not the standard characteristic defining a typical pipe coupling. Therefore, having inside threads on both ends is the defining feature of a pipe coupling.