The union is a stainless steel 304 cast pipe fitting with female National Pipe Taper (NPT) threads for connecting and extending two male threaded pipes. The union has three pieces and includes a threaded connection that can be screwed or unscrewed to connect or disconnect pipes more easily than couplings. It has NPT threads on both ends for creating tighter seals than straight threads. Pipe fittings are components used for connecting, terminating, controlling flow, and changing the direction of piping in many different industries. When purchasing pipe fittings, consider the application, as this will affect material type, shape, size and required durability. Fittings are available threaded or unthreaded, in many shapes, styles, sizes, and schedules (pipe wall thickness).