Heavy durable brass extension piece male-female, it is a threaded fitting  used to extend the length from the terminal point of water supply to the tap. It consists of a cylinder with male thread on one end and female thread in the other one of the same dimension. Also, it is corrosion resistant in wet, electrically conductive, and non-magnetic environments. This product comes with thread dimensions of 1/2", and with extension length from 1 cm to 5 cm. The most common application is to mount wall taps, in cases where the connection point is far from the point of tap installation.