5100 Series Low Spill Connect Under Pressure Dust Plug, -20 Coupling Size(s)

Up to 500 psi, yes. The 5100 Series dust plug is built to connect even when the line is under pressure, so you don't have to bleed the system down before making the connection. That's one of the main reasons this plug gets used in active hydraulic systems where shutting everything down just to swap a fitting isn't practical.