Sprocket remover. I forced it a bit, and the chain came off once. I reattached it and it works, but the attachment condition isn't very good, so I'm selling it to replace it. I think it can be fixed if you use a quick pin or junk chain etc. well. ⚠️Please purchase if you understand that it is junk. Shipping is planned via Yu-Packet Post. #Roadbike #Bicycle #Crossbike #Sprocket #Tool #Junk #noguti #Bike #Mountainbike Thank you for viewing.