Which statement correctly describes AN vs AC fittings?

• A. AN fittings have a shoulder between the flare cone end and the first thread.
• B. AC fittings have a shoulder between the flare cone end and the first thread.
• C. AN fittings extend threads to the flare cone.
• D. AC fittings are all steel.

Answer: (A)

The main difference between AN and AC flare fittings is where the flare seats relative to the threaded portion. AN fittings have a distinct shoulder between the flare cone end and the first thread. That shoulder provides a seating surface for the flare and helps locate and seal the tube properly when the nut is tightened. In contrast, AC fittings don’t have that shoulder in that location, and the flare seating is arranged differently.

So, the statement about AN fittings having a shoulder between the flare cone end and the first thread is the correct description. The other options misstate how the flare seats or generalize materials in a way that isn’t accurate for all AC fittings.