Fine or not? 4a,b or c?

Curly Bola asked me about the thickness of my strands recently and I had no idea. I feel it’s fine and not thick because of how fragile it is. But could it be medium? Not sure. I haven’t had much success searching the Internet so if you have suggestions on how I can tell, pls share


My hair strand in a stretched is between the 2 pieces of thread.  And then there is a strand in the unstretched state.  It’s like a pen coil so is that 4a, b, c? 🙂