The sellers said this: This machine takes round bobbins, and includes one in the machine along with the bobbin holder. If you need a new head for your old treadle, this can also run by treadle by removing the motor and attaching it into your cabinet.
The only problems we know with this machine is that the rubber wheel for the bobbin rewinder is cracking, but still in one piece. Also, the rubber drive wheel attached to the motor is a little loose and can't be tightened. However, when the motor us spun up, it pulls into the drive wheel on the machine and makes good contact.
All I know is that when I plugged it in it went crazy going up and down and then it seized up and started to smell.