We call them Pouch Studs, but they're also known as Sam Brown studs, ball post studs, screwback round head posts, or just those little things that look a bit like a mushroom. The stud is held in place with a small screw, then simply make a keyhole shaped hole in the leather to be fixed over the ball-shaped head, and you have a minimalist closure for a pouch, or a belt attachment. Antique finish with a 13mm long stem.