I picked one up a couple of weeks ago and have not used it yet. It is a sole plate for the walking foot. I have the box right here......It is not a foot so there is no number on it... the part number written in small print is .32913.70.00 Price on mine was $33.43 but it got it 20% off because my store is closing. They just say it is an "Interchangeable sole with guiding plate for the walking foot 50"