HK Series Industrial Interchange Series B StainlessSteel Hydraulic Quick Disconnect, Female Half, -04 Coupling, 1/4-18 Female NPT

Stainless steel construction gives it noticeably better corrosion resistance than carbon steel alternatives, which matters a lot when you're dealing with moisture, mild chemicals, or fluids that would chew through standard hardware over time. The Buna-N seals are rated from -40 degrees F up to 250 degrees F, so you've got solid range for most general hydraulic and fluid transfer applications. For harsher chemical exposure, seal material is worth checking since Viton and EPR options exist for this series depending on the fluid compatibility you need.

It’s the female socket half in the HK Series with a -04 coupling size and a 1/4-18 female NPTF pipe thread connection.

You'll find these couplings used in all sorts of places, from farm equipment and construction to chemical plants and even aerospace applications. They're made tough to handle a lot of different fluids and conditions.