This steel brake adapter has a male 3/8-24 flat-faced fitting on the short end and a standard 3AN male (3/8-24, 37° convex) on the other end. The 9/16" hex is designed to be used with a 3/8" Crush Washer (Part No. 3241-3/8, sold separately) when sealing the 3/8-24 side against a flat faced port. The 3/8-24 end has no other provision for sealing. 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.