Hi-flow  brass compression fittings are made from high quality UNS CA-360 brass bar.   Common Application:  instrumentation, hydraulic and pneumatic systems.  Pressure rating is based on the tubing used. For vibration issues use a  long nut.  Use With:  aluminum, copper and plastic tubing.  Plastic tubing usually requires internal tube support.  Tube size is measured by the  outside diameter of tubing used.