The unit is plastic with a small leaf spring. Flat blade (despite optical illusion in attached photo) on top travels inside window track to catch interior stops, holding window open at various heights. At the bottom, the latch broadens out to provide a thumb platform allowing latch to be squeezed against spring, disengaging top hook from interior stops to raise or lower window.
We have a some of these latches snapped, and a greater number that are simply missing their bottom springs.
Sorry I did not measure these when I had them out, but I did include a quarter in the photo for approximate size.
