M9-HP4 Adapter 9/16-18 to 1/4" H.P. with Max Working Pressure of 50,000 PSI
First Thread: 1/4" HP (high Pressure)
Second Thread: M9 (9/16-18)
Max Working Pressure: 50,000 PSI (3447 Bar)
These are common adapters for making a connection between a high pressure chart recorder and its hose.