>>8589643Alright I went further. I took a picture of my Trap-Jaw's arm. There's like a lip that comes out on the joint so it sockets into the torso's joint. This "lip" isn't on the hinged one, because it would get in the way and prevent the movement, hence the gap in the shoulder, and why the swivel one would sit flush with the torso. I'm very sure that all 4 of those are the hinge joint, because it's missing this "lip" which I circled.