That would be my guess, I have never seen anything like that before and I have never heard of gears in the hub. But that's all that come's to mind.Wild guess, as i've never actually seen one... but based on hub diameter, and single sprocket, is that a rear hub with multiple gears built into it? A 3-speed maybe? What happens when you actually try to use it? I assume you've actually tried riding it and flipping the lever to see what would happen?