Auto-Flo 23 Series, Aro 210 Interchange Multi-Series Coupling, Valved Female Half, -04 Coupling, 1/4-18 Female NPT

Aeroquip FD40 Series male halves connect directly to this coupling without any adapters. It also accepts male halves from the Aeroquip FD41 Series, Tru-Flate, and Parker Automotive. So if you're not sure which male half you're working with, that's actually one of the selling points here. It was put together with mixed-fleet situations in mind, where you might have a few different brands floating around the shop.