These are restricted oil fittings that go from a M12x1.5mm to a 4AN fitting. Engines with super high oil pressure need to be restricted but Holsets are very tolerant. If you do not want restricted oil flow, you can drill out the fitting or find a supplier for an "adapter" rather than a turbo fitting. Please due your own due diligence on whether your turbo needs a restricted fitting based on the oil supply of your engine. These fittings will fit on the HX30, HX35 and HE351 we supply.
Below are some lines from the HX30 repair manual to help with the decision on whether to run a restricted fitting:
13. The minimum oil pressure when the engine is on load must be 210 kPa (30 lbf/in2). Maximum permissible operating pressure is 500 kPa (72 lbf/in2) although 600 kPa (88 lbf/in2) is permitted during cold start up. Under idling conditions pressure should not fall below 70 kPa (10 lbf/in2).
14. Recommended oil flows for the turbochargers are 2 litre/min at idle and 3 litre/min above maximum torque speed.