Brass Push>Connect Tube Fitting, 0.31 Inch Tube OD Union

Pressure capacity on push-to-connect fittings like this one does vary based on the tube outer diameter being used. The 250 psi rating is the ceiling for this fitting, but the actual working pressure in your setup depends on which tube size you pair it with. Smaller tubing generally holds pressure better than larger sizes at the same fitting, so your real-world limit may be lower depending on your configuration.