Air assist connector. Designed for direct connection of quick coupling and flex hose 1/4" thread with minimal stress on the printed model. I recommend inserting O ring 11/2 Printed without support. PETG / layer 0.1 !!! / perimeters 5x
https://www.aliexpress.com/item/1005004609099236.html
https://www.aliexpress.com/item/1005004598038376.html
The author marked this model as their own original creation.