exact items shown, GRC 874 to BNC adapter, used on RF meters and scopes from many manufacturers. Though we rarely see the 874 on new equipment, it's an excellent connector with good impedance matching across its intended operating frequencies. This is a panel mount type connector, the 874 would be on the outside, the BNC in the inside, the hole would be threaded to 7/8-16 threads, or there could be a nut.