Which of the following statements regarding flare fittings is correct?

The accurate statement regarding flare fittings is that AN fittings have an identifying shoulder. This shoulder plays a crucial role in the assembly and provides a visual cue that distinguishes AN fittings from other types of fittings. It ensures proper alignment and secures the connection when the fitting is torqued. This design feature is critical for ensuring the integrity of fluid transfer systems, especially in aerospace and automotive applications where pressure and safety are paramount.

In contrast, the other statements do not hold true. Not all flare fittings are identical in design; they can vary based on size, material, and specific applications. The claim that AC fittings are superior to AN fittings is misleading, as both fitting types serve different purposes and are designed according to different standards. Lastly, flare fittings are typically made from materials like brass or stainless steel, not plastic, as metal provides the necessary strength and durability for high-pressure applications. Thus, the assertion about AN fittings having an identifying shoulder accurately reflects a key characteristic that differentiates them in the realm of fluid systems.