This steel brake adapter has a male 3/8-24 flat-faced fitting on one short end and a 3AN male (3/8-24, 37° convex) on the other. The 9/16" hex is large enough to support a crush washer (sold separately) when sealing the 3/8-24 side against a flat faced port. Sold individually.
We also offer a 3AN Male to 3/8-24 Inverted Flare Adapter (Part No. 3265-2) for installations with an inverted flare (convex) seat in the female port.