A merchant coupling is a fitting used to join pipes, of similar size, together in a straight-line run. Merchant steel fittings are designed with Dryseal Taper Threads (NPTF) for more critical applications. NPTF Dryseal threads produce a mechanical seal by the mating and slight crushing of the threads when a wrench is applied to tighten the fittings.

Hex bushings are used to reduce the size of female threads from a larger to a smaller diameter. Hex Bushings are threaded fittings that have male threads on the outside and female threads on the inside with a hex head used to tighten the fitting into the threaded opening.