When NAPA or another auto parts store sell you a fitting, they don't know what your use is going to be. You can purchase the exact same fitting in Home Depot or Lowe's and again, they have no idea where it's being used. Will they work - sure. Are they safe - maybe. But - that brake system might have as high as 1000 or more psig during an emergency stop. Do you want to rely on, probably, a compromised braking system?
These old threads just keep reappearing