This is a side-release buckle or parachute buckle that works with 3/4 inch straps or 'webbing'.
I modeled this so I could print a replacement for a broken clip on my pack. Originally printed in PLA, which has been surprisingly functional so far, but I've reprinted in PET+ which has a much better flexible quality to it and should last far longer.
Prints best with support everywhere, especially for the female side of the buckle.
Is most functional when printed in PET+ or similar, but also works in ABS, PLA, etc.