GX16-4 4 Pin Plug and Socket Panel Connector.

Contacts Pin Number 4

Contacts Pin Diameter 2.5mm
Rated Voltage AC 250V
Rated Current 5A
Operating Voltage AC 250V
Withstand Voltage AC 1500V 
Insulator Resistance 1000 Ohm
Tube Hole Diameter 6.5mm
Thread Dia 16mm