Which family of fittings uses a 37-degree flare seating surface?

• A. Compression fittings
• B. JIC
• C. ORFS
• D. BSP

Answer: (A)

The seating geometry used to seal a hydraulic connection is what this question tests. A 37-degree flare seating surface is a hallmark of JIC fittings. The male flare end is machined with a 37-degree conical surface that mates with a precisely shaped female flare seat, and when the nut is tightened, this cone meets the seat to form a strong metal-to-metal seal suitable for high-pressure and vibration-heavy systems.

Compression fittings seal differently: they rely on deforming a ferrule against the tubing and the fitting body, not on a conical flare seat. ORFS uses an O-ring on the face of the connection, so the seal is provided by the O-ring on a flat seating surface rather than by a flare cone. BSP relies on threaded interfaces (and sometimes a separate seat) rather than a 37-degree flare geometry.